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Proving properties of curves - class-XI

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If slope of tangent of curve $y=\dfrac{x}{b-x}$ at $(1,1)$ be $2$ then $b=$

  1. $1$

  2. $2$

  3. $0$

  4. $-1$

  5. $-2$


Correct Option: B
Explanation:

Given,

$y=\dfrac{x}{b-x}$
Now,
$\dfrac{dy}{dx}=\dfrac{(b-x)1+x.(-1)}{(b-x)^2}$
or, $\dfrac{dy}{dx}=\dfrac{b}{(b-x)^2}$.
Now,
$\left.\dfrac{dy}{dx}\right| _{(1,1)}=\dfrac{b}{(b-1)^2}$.
According to the problem,
$\dfrac{b}{(b-1)^2}=2$
or, $b=2(b^2-2b+1)$
or, $2b^2-5b+2=0$
or, $(2b-1)(b-2)=0$
or, $b=\dfrac{1}{2}, 2$.

The general solution of the differential equation $\sin{2x}\left( \cfrac { dy }{ dx } -\sqrt { \tan { x }  }  \right) -y=0$ is $y\phi(x)=x+c$ then ${ \Phi  }^{ 1 }\left( \cfrac { \pi  }{ 4 }  \right) $ is _____

  1. $1$

  2. $-1$

  3. $\cfrac{1}{\sqrt{3}}$

  4. $\sqrt{-3}$


Correct Option: B
Explanation:

$\displaystyle \frac{dy}{dx}-\text{cosec}2x y=\sqrt{\tan x};I.F=e^{\displaystyle \int-\text{cosec}2xdx}$

$=\sqrt{\text{cosec }2x+\text{cot} 2x} \implies y\sqrt{\text{cosec}2x+\text{cot}2x}=x+c\implies \phi'\bigg(\frac{\pi}{4}\bigg)=-1$

The derivative of a differentiable even function is always an even function.

  1. True

  2. False


Correct Option: B
Explanation:

The statement is false.

For example take the function,
$f(x)=\sin^2 x$, $x\in \mathrm{R}$.
This function is even as $f(-x)=f(x)\forall x\in\mathrm{R}$.
But the derivative of $f(x)$, $f'(x)=-2\sin x.\cos x$, $x\in \mathrm{R}$..
This function $f'(x)$ is not even.
As $f'(-x)=-f'(x)$, $\forall x\in \mathrm{R}$.

If $g$ is the inverse of $f$ and $\displaystyle f'\left( x \right) =\frac { 1 }{ 1+{ x }^{ 3 } } $, then $g'\left( x \right) $ is equal to

  1. $1+{ \left[ g\left( x \right) \right]  }^{ 3 }$

  2. $\displaystyle \frac { 1 }{ 1+{ \left[ g\left( x \right) \right]  }^{ 3 } } $

  3. ${ \left[ g\left( x \right)  \right]  }^{ 3 }$

  4. None of these


Correct Option: A
Explanation:

We have, $g=$inverse of $f={ f }^{ -1 }$

$\Rightarrow g\left( x \right) ={ f }^{ -1 }\left( x \right) \Rightarrow f\left[ g\left( x \right)  \right] =x.$
Differentiating w.r.t. $x,$ we get
$f'\left[ g\left( x \right)  \right] .g'\left( x \right) =1$
$\displaystyle \therefore g'\left( x \right) =\frac { 1 }{ f'\left[ g\left( x \right)  \right]  } =1+{ \left[ g\left( x \right)  \right]  }^{ 3 }$
$\displaystyle \left[ \because f'\left( x \right) =\frac { 1 }{ 1+{ x }^{ 3 } } ,\therefore f'\left[ g\left( x \right)  \right] =\frac { 1 }{ 1+{ \left[ g\left( x \right)  \right]  }^{ 3 } }  \right] $

If $y=mx+c$ is the normal at a point $(8,8)$  on the parabola ${ y }^{ 2 }=8x$ Find $m$

  1. $-2 $

  2. $8 $

  3. $10 $

  4. $16 $


Correct Option: A
Explanation:

Given equation $y^2=8x $

Slope of tangent is given as $2y\dfrac{dy}{dx}=8\\dfrac{dy}{dx}=\dfrac{4}{y}\\left.\dfrac{dy}{dx}\right| _{(8,8)}=\dfrac{4}{8}=\dfrac 1{2}$
Slope of normal is $\dfrac{-1}{\dfrac{1}{2}}=-2$

Function $ f(x)= \sin^{-1} (3x-4x^3) $ is-

  1. Always differentiable

  2. Not differentiable at 2 points

  3. Not continuous at 2 points

  4. Not differentiable at 3 points


Correct Option: B
Explanation:

Given the function 

$f(x)=\sin^{-1}(3x-4x^3)=3\sin^{-1}x$.
We have $f'(x)$ does not exists at two points and they are $x=\pm 1$ as $f'(x)=\dfrac{1}{\sqrt{1-x^2}}$ for $x\in (-1,1)$.
So option (B) is correct.

If $\log \sqrt{x^2+y^2}=\tan^{-1}\left(\dfrac{y}{x}\right)$ , then $\dfrac{dy}{dx}$ is:

  1. $1$

  2. $2$

  3. $\dfrac{2x}{\sqrt{x^2+y^2}}$

  4. $\dfrac{x+y}{x-y}$


Correct Option: D
Explanation:
Given, 
$\log\sqrt{x^2+y^2}=\tan ^{-1}\left(\dfrac{y}{x}\right)$
Now, differentiating both sides w.r.to $x$ we get,
or, $\dfrac{1}{2}\dfrac{2x+2y\dfrac{dy}{dx}}{x^2+y^2}=\dfrac{x^2}{x^2+y^2}.\left(-\dfrac{y}{x^2}+\dfrac{\dfrac{dy}{dx}}{x}\right)$
or, $x+y\dfrac{dy}{dx}=-y+x\dfrac{dy}{dx}$
or, $(x-y)\dfrac{dy}{dx}=(x+y)$
or, $\dfrac{dy}{dx}=\dfrac{x+y}{x-y}$

Average Speed and Instantaneous speed are the same things.

  1. True

  2. False


Correct Option: B
Explanation:

False.
An average speed tells how much distance a body covers during a certain time span, but it does not tell much about the actual motion that occurred. Instantaneous speed is the exact speed that a body is moving at, at a given instant in time. It is a true measure of the body's motion for that point in time.

If $y = \left| {\cos x} \right| + \left| {\sin x} \right|$ , then ${\dfrac{dy} {dx}}$ at $x = {\dfrac {2\pi } 3}$ is

  1. ${1 \over 2}\left( {\sqrt 3 + 1} \right)$

  2. $2\left( {\sqrt 3 - 1} \right)$

  3. ${1 \over 2}\left( {\sqrt 3 - 1} \right)$

  4. none of these


Correct Option: A
Explanation:

$y=|\cos x|+|\sin x|$


at  $x=\dfrac{2\pi}{3},$

$y=-\cos x+\sin x$

$now, \dfrac{d{y}}{d{x}}=\sin x+\cos x$

$\dfrac{d{y}}{d{x}}=\sin\dfrac{2\pi}{3} +\cos \dfrac{2\pi}{3}$

$ \dfrac{d{y}}{d{x}}=\dfrac{\sqrt{3}}{2}+\dfrac{1}{2}$

$ \dfrac{d{y}}{d{x}}=\dfrac{1}{2}(\sqrt{3}+1)$

The line $y =\sqrt{2}x + 4\sqrt{2}$ is a normal to $y^{2} =4ax$ then a = 

  1. $2$

  2. $\sqrt{2}$

  3. $1$

  4. $-1$


Correct Option: D
Explanation:

The general form of equation of normal to the parabola $y^2=4ax$ is $y=mx-2am-am^3$.....(1) where $m$ is the slope of the normal.

According to the problem, $y =\sqrt{2}x + 4\sqrt{2}$.....(2) is the normal to the parabola.
Equation (1) and (2) are identical.
Then $m=\sqrt{2}$ and $-2am-am^3=4\sqrt{2}$ or, $a(-2\sqrt{2}-2\sqrt{2})=4\sqrt{2}$ or, $a=-1$ [ Using the value of $m$].
So $a=-1$.

The  number of points where $f(x) = \mid | x |^2 - 5| x | + 6 \mid $ is non-derivable is/are

  1. 1

  2. 3

  3. 4

  4. 5


Correct Option: D
Explanation:

Let $\mid x \mid = t$

$f(x) = \mid t^2 -5t +6 \mid = \mid t(t-3) -2(t - 3)\mid = \mid (t - 3)(t - 2)\mid$
$\Rightarrow f(x) = \mid (\mid x\mid - 3)(\mid x\mid -2)\mid$
Non-derivable at all $x$ where $f(x) = 0$
$\pm 3, 0, \pm 2$
Hence $5.$

State whether the given statement is True or False.
A function is said to be differentiable in an interval $(a, b)$, if it is differentiable at every point of $(a, b)$.

  1. True

  2. False


Correct Option: A
Explanation:

Consider the function as $f(x)$.
A function $f(x)$ is differentiable on an interval if the derivative exists for each point in that interval.
Hence, a function is said to be differentiable in an interval $(a,b)$, if it is differentiable at every point of $(a,b)$.
Therefore, the given statement is true.

Let $f(x) = \left{\begin{matrix} 2 + 1,& x \leq 1\ x^{2} + 2, & 1 < x \leq 2\ 4x - 2, & x > 2\end{matrix}\right.$ then the number of points where $f(x)$ is non-differentiable, is equal to

  1. $0$

  2. $1$

  3. $2$

  4. $3$


Correct Option: B
Explanation:
$f'(1^-)=0$ and 
$f'(1^+)=2x=2$
Hence $f(x)$ is not derivable at $x=1$

$f'(2^-)=2x=4$ and 
$f'(2^+)=4$
Hence $f(x)$ is derivable at $x=2$


So, $f(x)$ is non-differentiable at only $1$ point.

$f(x)=|\cos x|$ is not differentiable for the points given by $x=?$

  1. $\dfrac{\pi}{2}$

  2. $(2n+1)\pi, \forall n\in I$

  3. $(2n+1)\dfrac{\pi}{2}\forall n\in I$

  4. $0$


Correct Option: A

If $g$ is the inverse of $f$ and $f'(x)=\dfrac{1}{1+x^{3}}$, then $g'(x)$ is equal to.

  1. $1+[g(x)]^{3}$

  2. $\dfrac{1}{1+[g(x)]^{3}}$

  3. $[g(x)]^{3}$

  4. $None\ of\ these$


Correct Option: A
Explanation:
Here, $f'(x)=\dfrac{1}{1+x^3}$
$\Rightarrow$  $g$ is inverse of function $f$, then
$f[g(x)]=x$
Differentiating w.r.t $x,$
$f'[g(x)]\times g'(x)=1$

So $g'(x)=\dfrac{1}{f'[g(x)]}$

$\therefore$  $g'(x)=1+[g(x)]^3$

If $f(x)=(x^2-4)\left|x^3-6x^2+11x-6\right|+\dfrac{x}{1+|x|}$, then the set of points at which the function $f(x)$ is not differentiable is?

  1. ${-2, 2, 1, 3}$

  2. ${-2, 0, 3}$

  3. ${-2, 2, 0}$

  4. ${1, 3}$


Correct Option: D
Explanation:


$\\f(x)=(x^2-4)|(x-1)(x^2-5x+6)|+(\frac{x}{1+|x|})\\=(x^2-4)|(x-1)(x-2)(x-3)|+(\frac{x}{1+|x|})$

|x| functions are not differentiable, at points where their value becomes zero because at these points it has sharp corners.

so at x=1, 2, 3 are possible points where it might not be differentiable but at x=2, it is multiplied by term $(x^2-4)$ which gives value zero and hence will neutralise the effect, so only at x={1, 3}, f(x) is not differentiable.

 

If $\sqrt { { x }^{ 2 }+{ y }^{ 2 } } ={ e }^{ t }$ where $t=\sin ^{ -1 }{ \left( \cfrac { y }{ \sqrt { { x }^{ 2 }+{ y }^{ 2 } }  }  \right)  } $ then $\cfrac { dy }{ dx } $ is equal to

  1. $\cfrac { x-y }{ x+y } $

  2. $\cfrac { x+y }{ x-y } $

  3. $\cfrac { y-x }{ y+x } $

  4. $\cfrac { x-y }{ 2x+y } $


Correct Option: B
Explanation:
$t=\sin ^{ -1 }{ \left( \cfrac { y }{ \sqrt { { x }^{ 2 }+{ y }^{ 2 } }  }  \right)  } $, differentiate on both sides.
$\cfrac { dt }{ dx } =\cfrac { 1 }{ \sqrt { 1-{ \left( \cfrac { y }{ \sqrt { { x }^{ 2 }+{ y }^{ 2 } }  }  \right)  }^{ 2 } }  } \cfrac { d\left( \cfrac { y }{ \sqrt { { x }^{ 2 }+{ y }^{ 2 } }  }  \right)  }{ dx } \quad \left( \because \cfrac { d\left( \sin ^{ -1 }{ x }  \right)  }{ dx } =\cfrac { 1 }{ \sqrt { 1-{ x }^{ 2 } }  }  \right) $
$=\left( \cfrac { \sqrt { { x }^{ 2 }+{ y }^{ 2 } }  }{ x }  \right) \left[ \cfrac { \left( \sqrt { { x }^{ 2 }+{ y }^{ 2 } }  \right) \cfrac { dy }{ dx } -\left( \cfrac { 2x+xy\cfrac { dy }{ dx }  }{ x\sqrt { { x }^{ 2 }+{ y }^{ 2 } }  }  \right) y }{ \left( { x }^{ 2 }+{ y }^{ 2 } \right)  }  \right] $
$=\left( \cfrac { \sqrt { { x }^{ 2 }+{ y }^{ 2 } }  }{ x }  \right) \left[ \cfrac { \left( { x }^{ 2 }+{ y }^{ 2 } \right) \cfrac { dy }{ dx } -\left( xy+{ y }^{ 2 }\cfrac { dy }{ dx }  \right)  }{ \left( { x }^{ 2 }+{ y }^{ 2 } \right) \sqrt { { x }^{ 2 }+{ y }^{ 2 } }  }  \right] $
$\therefore \cfrac { dt }{ dx } =\cfrac { { x }^{ 2 }\cfrac { dy }{ dx } -xy }{ x\left( { x }^{ 2 }+{ y }^{ 2 } \right)  } =\cfrac { x\cfrac { dy }{ dx } -y }{ { x }^{ 2 }+{ y }^{ 2 } } $
Given that $\sqrt { { x }^{ 2 }+{ y }^{ 2 } } ={ e }^{ t }$
${ x }^{ 2 }+{ y }^{ 2 }={ e }^{ 2t }$ differentiate on both sides
$2xx+2y\cfrac { dy }{ dx } ={ e }^{ 2t }\left( 2 \right) \cfrac { dt }{ dx } $
$x+y\cfrac { dy }{ dx } =\left( \quad { x }^{ 2 }+{ y }^{ 2 } \right) \left( \cfrac { x\cfrac { dy }{ dx } -y }{ { x }^{ 2 }+{ y }^{ 2 } }  \right) $
$x+y=(x-y)\cfrac { dy }{ dx } $
$\therefore \cfrac { dy }{ dx } =\cfrac { x+y }{ x-y } $

Value of c is :-
$\dfrac{d}{dx}(c\ ^{f(x)}) = f' (x)e^{f(x)}$

  1. $e$

  2. $e^2$

  3. $1$

  4. $ln{x}$


Correct Option: A
Explanation:

$\dfrac{d}{dx}(C^{f(x)}) = f(x) . e^{f(x)}$

$C^{f(x)} . ln C. f(x) = f(x) . e^{f(x)}$
$C^{f(x)} , ln (C) = e^{f(x)}$
$ln\ C = 1$
$C = e$

The condition that the line $\dfrac{x}{a}+\dfrac{y}{b}=1$ is tangent to the curve $x^{2/3}+y^{2/3}=1$ is

  1. $a^{2}+b^{2}=2$

  2. $a^{2}+b^{2}=1$

  3. $\dfrac{1}{a^{2}}+\dfrac{1}{b^{2}}=1$

  4. $a^{2}$


Correct Option: A

If line $PQ$, whose equation is $y = 2x + k,$  is a normal to the parabola whose vertex is   $(-2,3)$ and the axis parallel to the $x$-axis with latus rectum equal to $2$, then the possible value of k is

  1. $\dfrac{{58}}{8}$

  2. $\dfrac{{50}}{8}$

  3. $1$

  4. $-1$


Correct Option: C
Explanation:
Normal to parabola $\rightarrow y=2x+k$
parabola $\rightarrow (y-3)^{2}=4a(x+2)$
Latus rectum$=2$
$4a=2$
$a=\dfrac{1}{2}$
parabola $\rightarrow (y-3)^{2}=2(x+2)$
$y=3+\sqrt{2}\sqrt{x+2}$
slope of normal =$\dfrac{1}{-y'}$
$y'=\dfrac{\sqrt{2}}{2\sqrt{x+2}}=\dfrac{1}{\sqrt{2x+4}}$
$m=-\sqrt{-2x+4}$
if $2=-\sqrt{2x+4}$
then $x=0, y=5, 1$
$(0,5$) should also lies on $y=2x+k$
then
$k=5,1$
$C$ is correct

If $y = \dfrac { 1 } { 1 + x ^ { n - m } + x ^ { p - m } } + \dfrac { 1 } { 1 + x ^ { m - n } + x ^ { p - n } } + \dfrac { 1 } { 1 + x ^ { m - p } + x ^ { n - p } }$ then $\dfrac { d y } { d x }$ at $x = e ^ { m ^ { n p } }$ is equal to

  1. $e ^ { m n p }$

  2. $e ^ { m n / p }$

  3. $e ^ { n p / m }$

  4. $0$


Correct Option: D
Explanation:
$\\y=(\dfrac{1}{1+(\dfrac{x^n}{x^m})+(\dfrac{x^p}{x^m})})+(\dfrac{1}{1+(\dfrac{x^m}{x^n})+(\dfrac{x^p}{x^n})})+(\dfrac{1}{1+(\dfrac{x^m}{x^p})+(\dfrac{x^n}{x^p})})$

$\\=(\dfrac{x^m}{x^m+x^n+x^p})+(\dfrac{x^n}{x^n+x^m+x^p})+(\dfrac{x^p}{x^p+x^m+x^n})$

$\\=(\dfrac{x^m+x^n+x^p}{x^m+x^n+x^p})$

$\\=1$
$\\\therefore\>(\dfrac{dy}{dx})=0$

Let f(x) be a differentiable function and $f\left( \alpha  \right) = f\left( \beta  \right) = 0\,\left( {\alpha  < \beta } \right)$, then in the interval $\left( {\alpha ,\beta } \right)$

  1. $f\left( x \right) + f'\left( x \right) = 0$ has at least one root.

  2. $f\left( x \right) - f'\left( x \right) = 0$ has at least one root.

  3. $f\left( x \right) . f'\left( x \right) = 0$ has at least one root.

  4. None of these


Correct Option: C
Explanation:

$\therefore f(\alpha) = f(\beta) = 0$


Thus, By Rolle's theorem
($\because f(x)$ is a differential function)
$f'(c) = 0$     where $\in (\alpha, \beta)$

$\therefore $ In the interval $(\alpha, \beta)$ 
$f(x) . f'(x) = 0$ has at least one root.

If $y = \log \left( \frac { 1 + x } { 1 - x } \right) ^ { 1 / 4 } - \frac { 1 } { 2 } \tan ^ { - 1 } x ,$ then $\frac { d y } { d x } =$

  1. $\frac { x ^ { 2 } } { 1 - x ^ { 4 } }$

  2. $\frac {2 x ^ { 2 } } { 1 - x ^ { 4 } }$

  3. $\frac { x ^ { 2 } } { 2 \left( 1 - x ^ { 4 } \right) }$

  4. None of these


Correct Option: A
Explanation:

$\dfrac{dy}{dx}=\dfrac{1}{(\dfrac{1+x}{1-x})^{\frac{1}{4}}}\times$ $\dfrac{1}{4\times{(\dfrac{1+x}{1-x})^{\frac{3}{4}}}}\times $ $\dfrac{(1-x)(1)-(1+x)(-1)}{(1-x)^{2}}-$ $\dfrac{1}{2}\dfrac{1}{x^2+1}$ 


$\dfrac{1-x}{4(1+x)}\times\dfrac{2}{(1-x)^2}$ $-\dfrac{1}{2(x^2+1)}$  $=\dfrac{1}{2(1-x^2)}-$ $\dfrac{1}{2(x^2+1)}$ =$\dfrac{x^2}{1-x^4}$

If f'$\left( x \right) =\sqrt { { 2x }^{ 2 }-1 } $ and y=f$\left( { x }^{ 2 } \right) $ then $\dfrac { dy }{ dx } $ at x=1 is

  1. 2

  2. 1

  3. -2

  4. none of these


Correct Option: D
Explanation:

We have,

$f\left( x \right)=\sqrt{2{{x}^{2}}-1}$

And

$ y=f\left( {{x}^{2}} \right) $

$ y={{\left( \sqrt{2{{x}^{2}}-1} \right)}^{2}} $

$ y=2{{x}^{2}}-1 $


On differentiating and we get,

$ \dfrac{dy}{dx}=\dfrac{d}{dx}\left( 2{{x}^{2}}-1 \right) $

$ \dfrac{dy}{dx}=4x-0 $

$ \dfrac{dy}{dx}=4x $

At point $\left( x=1 \right)$

So,

$ \dfrac{dy}{dx}=4x=4\left( 1 \right) $

$ \dfrac{dy}{dx}=4 $

Hence, this is the answer.

A differentiable function function $y = h(x)$ satisfies $\displaystyle \overset{x}{\underset{0}{\int}} (x - t + 1)h(t)dt = x^4 + x^2; \forall x \ge 0$, then value of $h(0) + h'(0)$ is equal to

  1. $0$

  2. $1$

  3. $e^2$

  4. $2$


Correct Option: A

Area of the triangle formed by the lines $x-y=0, x+y=0$ and ant tangent to the hyparabola $x^{2}-y^{2}=a^{2}$ is 

  1. $|a|$

  2. $\dfrac{1}{2}|a|$

  3. $a^{2}$

  4. $\dfrac{1}{2}a^{2}$


Correct Option: C
Explanation:

Equation of line

$ x-y=0\,\,......\,\,\left( 1 \right) $

$ x+y=0\,\,.......\,\,\left( 2 \right) $


Equation of hyperbola is

${{x}^{2}}-{{y}^{2}}={{a}^{2}}\,\,......\,\,\left( 3 \right)$


Let the point $P(a\sec \theta, a\tan \theta)$ on the hyperbola.


Equation of tangent is,

$ x{{x} _{1}}-y{{y} _{1}}={{a}^{2}} $

$\Rightarrow a(x\sec \theta-y\tan\theta)=a^2$

$ \Rightarrow x\sec \theta -y\tan \theta =a\,\,......\,\,\left( 4 \right) $


Now,

Area of $\Delta AOB$ $=\dfrac{1}{2}$

$=\dfrac{1}{2}\left|a^2(\tan^2\theta-\sec^2\theta)-a^2(\sec^2\theta-\tan^2\theta)\right|$

$ =\dfrac{1}{2}\left| {{a}^{2}}\left( -1 \right)-{{a}^{2}}\left( 1 \right) \right| $

$ =\dfrac{1}{2}\left| -2{{a}^{2}} \right| $

$ =\left| -{{a}^{2}} \right| $

$ =\left| {{a}^{2}} \right| $


Hence, this is the answer.

If $x = \exp \left{ \tan ^ { - 1 } \left( \frac { y - x ^ { 2 } } { x ^ { 2 } } \right) \right}$ then $\frac { d y } { d x } =$

  1. $2 x [ 1 + \tan ( \log x ) ] + x \cdot \sec ^ { 2 } ( \log x )$

  2. $x [ 1 + \tan ( \log x ) ] + \sec ^ { 2 } ( \log x )$

  3. $2 x [ 1 + \tan ( \log x ) ] + x ^ { 2 } \sec ^ { 2 } ( \log x )$

  4. None of these


Correct Option: D
Explanation:
$x=exp\left\{\tan^{-1}\left(\dfrac{y-x^2}{x^2}\right)\right\}$
$ln x=\tan^{-1}\left(\dfrac{y-x^2}{x^2}\right)$
$\Rightarrow \tan (ln x)=\dfrac{y}{x^2}-1$
$\Rightarrow y=x^2[\tan (ln x)+1]$
$=x^2\tan(ln x)+x^2$
$\dfrac{dy}{dx}=2x\tan (ln x)+x^2\sec^2(ln x)\dfrac{1}{x}+2x$
$=2x\tan (ln x)+x\sec^2(ln x)+2x$.

Consider the function $f(x)=\mathrm{s}\mathrm{g}\mathrm{n} x$ and $g(x)=x\left ( 1-x^{2} \right )$. Which of the following does NOT hold good?

  1. $(fog)(x)$ is neither odd nor even

  2. $(gof)(x)$ is odd

  3. $(fog)(x)$ is neither continuous nor differentiable for some $x$ on $\left ( -\infty, \infty \right )$

  4. $(fog)(x)$ is continuous and differentiable for every $x$ on $\left ( -\infty, \infty \right )$


Correct Option: A,C
Explanation:

 $\text{sgn}(x) =\begin{cases}-1 & x <0\0 & x = 0\ 1 & x>0\end{cases} $
$g(x)=x(1-x^{2})$
$=x(1-x)(1+x)$
$g(x)=0$ implies, $x={-1,0,1}$.
$\text{sgn}(g(x))=\begin{cases}-1 & x\in(-\infty,-1)\cup(1,\infty) \0 & x =  \big{-1,0,1\big} \ 1 & x\in(-1,1)\end{cases} $

The set of all points of differentiability of the function $\displaystyle f(x) = \dfrac{\sqrt{x + 1} 1}{\sqrt{x}}$ for $x$  and $f(0)$ = 0 is

  1. $(\infty , \infty)$

  2. $[0 , \infty)$

  3. $(0 , \infty)$

  4. $(\infty$ , $\infty)$ $-\left { 0 \right }$


Correct Option: C

If the graph of the equation $y = 2x^2 - 6x + C$ is tangent to the $x$-axis, the value of $C$ is

  1. $3$

  2. $3\dfrac{1}{2}$

  3. $4$

  4. $4\dfrac{1}{2}$

  5. $5$


Correct Option: D
Explanation:

The derivative of given function is $4x-6 = 0$, which gives $x = \dfrac {3}{2}$
At $x$-axis , $y=0$ 

So, $0=2{\left (\dfrac {3}{2}\right)}^{2}-6\left (\dfrac {3}{2}\right)+C$
$\Rightarrow C = 9-\dfrac {9}{2}=\dfrac {9}{2} = 4\dfrac{1}{2}$

$f\left( x \right) =\begin{cases} x;\quad x<1 \ 3-x;\quad 1\le x\le 3 \end{cases}$ then $f^{'}(x)=$

  1. $2$

  2. $0$

  3. $-1$

  4. Does not exist


Correct Option: D
Explanation:

$f(x)=x ; x< 1$
$f(x)=3-x ; 1\leq x\leq 3$
If ${f}'(x) _{x\rightarrow 1^{-}}={f}'(x) _{x\rightarrow 1^{+}}={f}'(1)$
So, ${f}'(x) _{x\rightarrow 1^{-}}=1$
${f}'(x) _{x\rightarrow 1^{+}}=-1$
$\because {f}'(x) _{x\rightarrow 1^{-}}\neq {f}'(x) _{x\rightarrow 1^{+}}$
So, ${f}'(x)$ doesn't exist.

The domain of the derivative of the function
$\displaystyle f\left ( x \right )=\begin{cases}
\tan^{-1}x & \text{ if } \left | x \right |\leq 1 \
\frac{1}{2}\left ( \left | x \right |-1 \right ) & \text{ if } \left | x \right |> 1
\end{cases}$

  1. $R\sim \left { 0 \right }$

  2. $R\sim \left { 1 \right }$

  3. $R\sim \left { -1 \right }$

  4. $R\sim \left { -1, 1 \right }$


Correct Option: D
Explanation:

We have
$f\left ( x \right )=\begin{cases}
\left ( 1/2 \right )\left ( -x-1 \right ) & \text{ if } x< -1 \
\tan^{-1}x & \text{ if } -1\leq x\leq 1 \
\left ( 1/2 \right )\left ( x-1 \right ) & \text{ if } x> 1
\end{cases}$
Since $\displaystyle f\left ( -1 \right )=-\frac{\pi }{4}$, $\displaystyle f\left ( 1 \right )=\frac{\pi }{4}$ and $\lim _{x\rightarrow 1-}f\left ( x \right )=-1$, $\lim _{x\rightarrow 1+}f\left ( x \right )=0$
so f is not continuous at -1, 1, hence not differentiable at -1, 1. Also
$\displaystyle {f}'\left ( x \right )=\begin{cases}
-1/2 & \text{ if } x< -1 \
\frac{1}{1+x^{2}} & \text{ if } -1< x< 1 \
1/2 & \text{ if } x> 1
\end{cases}$
Thus the domain of ${f}'$ is $R - \left { -1, 1 \right }$.

Let $f(x)=ax^2+bx+c$ such that $f(1)=f(-1)$ and a, b, c are in Arithmetic Progression.

Then find what kind of progression $f'(a), f'(b), f'(c)$ form.

  1. A.P.

  2. G.P.

  3. H.P.

  4. Arithmetico-geometric progression


Correct Option: A
Explanation:

The given equation is:


$ y= f(x) = ax^2 + bx + c$

Differentiating w.r.t to x we get,

$\Rightarrow y' = 2ax + b$

Since a, b, c are in A.P. we have, $2b = a + c$

$\Rightarrow b -a = c -b$

Finding the respective derivative values we get,

$y'(a) = 2a^2 + b$

$y'(b) = 2ab + b$

$y'(c) = 2ac + b$

Finding the common difference between the terms we get,

$y'(b) - y'(a) = (2ab + b) - (2a^2 + b)$

$\Rightarrow y'(b) - y'(a) = 2ab - 2a^2$

$\Rightarrow y'(b) - y'(a) = 2a(b -a)$

$\Rightarrow y'(b) - y'(a) = 2a(c -b)$

$y'(c) - y'(b) = (2ac + b) - (2ab + b)$

$\Rightarrow y'(c) - y'(b) = 2ac -2ab$

$\Rightarrow y'(c) - y'(b) = 2a(c-b)$


We got the same common difference between the three terms hence the derivatives are in A.P.         .....Answer

If $y=\displaystyle\dfrac{1}{a-z}$, then $\displaystyle\dfrac{dz}{dy}$ is:

  1. $(a-z)^2$

  2. $-(z-a)^2$

  3. $(z+a)^2$

  4. $-(z+a)^2$


Correct Option: A
Explanation:
$y=\dfrac{1}{a-z}$
$\dfrac{{d} y}{{d} z}=\dfrac{-1}{(a-z)^{2}}(-1)$   (By differentiating w.r.t z)
$\dfrac{{d} y}{{d} z}=\dfrac{1}{(a-z)^{2}}$
   $\therefore \dfrac{{d} z}{{d} y}=(a-z)^{2}$

Which of the following given statements is/are correct?

  1. If L.H.D $\neq $ R.H.D, then $f(x)$ is not differentiable at $x= c$

  2. If a function is differentiable at a point, it is necessarily continuous at the point.

  3. If a function is differentiable at each $x \in R$ then it is said to be every where differentiable.

  4. $\dfrac{d}{dx}(c f (x)) =c \dfrac{d}{dx} (f (x))$, where $c$ is a constant.


Correct Option: A,B,C,D
Explanation:

Using concept 1 we can say that Option A is correct.

It is mandatory that  at  a point where a function is differentiable, Left hand limit = Right Hand Limit. Thus, it is continuous at that point. therefore, Option B  is correct.
Option C is correct.
Using concept 2, we can  say  that option  D is  correct.

The value of $\displaystyle \frac{d}{dx} (|x-1|+ |x-5|) $ at x = 3 is

  1. -2

  2. 0

  3. 2

  4. 4


Correct Option: B
Explanation:

$\dfrac{d}{dx} |x| = \dfrac{|x|}{x}$


Applying the above formula ,

$\dfrac{d}{dx} ( |x-1|+|x-5|) = \dfrac{d}{dx}|x-1|+\dfrac{d}{dx}|x-5|= \dfrac{|x-1|}{x-1}+\dfrac{|x-5|}{x-5}$

Substituting $x=3$,

$\dfrac{|3-1|}{3-1}+\dfrac{|3-5|}{3-5} = \dfrac{|2|}{2} +\dfrac{|-2|}{-2} = \dfrac{2}{2} +\dfrac{2}{-2} =1-1 =0$

Let $f : R \rightarrow R$ be a function defined by $f(x)= \max\left { x,  x^3 \right }$. The set of all points where $f(x)$ is NOT differentiable is:

  1. ${-1, 1}$

  2. ${-1, 0}$

  3. ${0, 1}$

  4. ${-1, 0, 1}$


Correct Option: D
Explanation:

$ f(x)=m\left{ x, { x }^{ 3 } \right} $

$ =x;x<-1$ and
$ ={ x }^{ 3 };-1\le x\le 0$
$ \Rightarrow  f(x)=x;0\le x\le 1$ and
$={ x }^{ 3 };x\ge 1$
$ \therefore  f(x)=1;x<-1$
$ \therefore  f'(x)=3{ x }^{ 2 };-1\le x\le 0$ and $ =1$
$0<x<1$
Hence, option D is correct.

If $f(x) = \left{\begin{matrix}e^x+ax & x< 0 \ b(x-1)^2 & x \geq 0 \end{matrix}\right.$ is differentiable at $x= 0$, then $(a, b)$ is

  1. $(-3, -1)$

  2. $(-3, 1)$

  3. $(3, 1)$

  4. $(3, -1)$


Correct Option: B
Explanation:

Given that $f(x)$ is differentiable at $x=0$ , which implies $f(x)$ is continuous at $x=0$

$\Rightarrow b=1$
By using differentiable condition , we get ${e}^{0}+a=2b(0-1)$
$\Rightarrow 1+a=-2b=-2$
$\Rightarrow a=-3$
Therefore the correct option is $B$

If $f(x) =x[x \sqrt{x}-\sqrt{x+1}]$, then:

  1. $f(x)$ is continuous but not differentiable at $x= 0$

  2. $f(x)$ is not differentiable at $x= 0$

  3. $f(x)$ is differentiable at $x= 0$

  4. none of these


Correct Option: C
Explanation:

Given $f(x)= x^{2}\sqrt{x}-x\sqrt{x+1}$

$f^{ 1 }\left( x \right) =2x\sqrt { x } +\dfrac{x^2}{2\sqrt x} -\sqrt { x+1 } -\dfrac { x }{ 2\sqrt { x+1 }  } =\frac { 3 }{ 2 } x\sqrt { x } -\sqrt { x+1 } -\dfrac { x }{ 2\sqrt { x+1 }  } $
We get $f^{ 1 }\left( 0^{+} \right)=f^{ 1 }\left( 0^{-} \right) =-1$  
Therefore $f(x)$ is differentiable at $x=0$

If $y = \dfrac {1}{1 + x^{n - m} + x^{p - m}} + \dfrac {1}{1 + x^{m - n} + x^{p - n}} + \dfrac {1}{1 + x^{m - p} +x^{n - p}}$ then $\dfrac {dy}{dx}$ at $e^{m^{n^{p}}}$ is equal to

  1. $e^{mnp}$

  2. $e^{mn/p}$

  3. $e^{np/m}$

  4. $0$


Correct Option: D
Explanation:

$\quad \quad y=\cfrac { 1 }{ 1+{ x }^{ n-m }+{ x }^{ p-m } } +\cfrac { 1 }{ 1+{ x }^{ m-n }+{ x }^{ p-n } } +\cfrac { 1 }{ 1+{ x }^{ m-p }+{ x }^{ n-p } } \\ \Rightarrow y=\cfrac { 1 }{ 1+\cfrac { { x }^{ n } }{ { x }^{ m } } +\cfrac { { x }^{ p } }{ { x }^{ m } }  } +\cfrac { 1 }{ 1+\cfrac { { x }^{ m } }{ { x }^{ n } } +\cfrac { { x }^{ p } }{ { x }^{ n } }  } +\cfrac { 1 }{ 1+\cfrac { { x }^{ m } }{ { x }^{ p } } +\cfrac { { x }^{ n } }{ { x }^{ p } }  } $

$\Rightarrow y=\cfrac { { x }^{ m } }{ { x }^{ m }+{ x }^{ n }+{ x }^{ p } } +\cfrac { { x }^{ n } }{ { x }^{ m }+{ x }^{ n }+{ x }^{ p } } +\cfrac { { x }^{ p } }{ { x }^{ m }+{ x }^{ n }+{ x }^{ p } } $

$\quad \quad \quad =\cfrac { 1 }{ \left( { x }^{ m }+{ x }^{ n }+{ x }^{ p } \right)  } \left( { x }^{ m }+{ x }^{ n }+{ x }^{ p } \right) $

$\Rightarrow y=1\\ \Rightarrow \cfrac { dy }{ dx } =0\quad $ at all $x$

$\therefore \dfrac { dy }{ dx } $ at ${ e }^{  m ^ { n ^{ p } } }=0$

D answer

 

If the distance between a tangent to the parabola $y^{2} = 4x$ and a parallel normal to the same parabola is $2\sqrt{2}$, then possible values of gradient of either of them are:

  1. $-1$

  2. $+1$

  3. $-\sqrt{\sqrt{5} - 2}$

  4. $+\sqrt{\sqrt{5} - 2}$


Correct Option: A,B
Explanation:

$y=\frac { x }{ t } +at\ y=-xs+2as+a{ s }^{ 3 }\ s=-\frac { 1 }{ t } $

For parallel condition.
$ts=-1$

$\left| \dfrac { \left( 2as+a{ s }^{ 3 } \right) -\left( at \right)  }{ \sqrt { 1+{ s }^{ 2 } }  }  \right| =2\sqrt { 2 } \ \ \left| \dfrac { \left( 2as+a{ s }^{ 3 } \right) +\frac { a }{ s }  }{ \sqrt { 1+{ s }^{ 2 } }  }  \right| =\left| \dfrac { a\left( { s }^{ 4 }+2{ s }^{ 2 }+1 \right)  }{ s\sqrt { 1+{ s }^{ 2 } }  }  \right| =\left| \dfrac { a{ \left( { s }^{ 2 }+1 \right)  }^{ 2 } }{ s\sqrt { 1+{ s }^{ 2 } }  }  \right| =\left| \dfrac { a{ \left( { s }^{ 2 }+1 \right)  }^{ \frac { 3 }{ 2 }  } }{ s }  \right| $
As $a=1$
$\left| \dfrac { { \left( { s }^{ 2 }+1 \right)  }^{ \frac { 3 }{ 2 }  } }{ s }  \right| =2\sqrt { 2 } ={ 2 }^{ \frac { 3 }{ 2 }  }$
Putting $s$ as $\pm 1$ the above equation satisfies.
Hence, the answer is $1,-1$.

Consider the function $f(x)=\begin{cases} x^2 \sin \dfrac{1}{x};x\neq 0 \ 0 ; otherwise  \end{cases}$
then,

  1. $f$ is derivable at $x=0$

  2. $f $ is not derivable at $x=0$

  3. $f$ is derivable at $x=0$ and $f'(0)=0$

  4. $f$ is derivable at $x=0$ and $f'(0)\neq0$


Correct Option: A
Explanation:
Consider the function 
$f(x)=\begin{cases} x^{2}\sin\dfrac{1}{x}\ \ \ x\neq 0 \\ 0\ \ \ \ otherwise \end{cases}$
To check derivability at $x=0$
Concept : A function is derivable at $x=a$ if
$LHD \, at(x=a)=RHD\, at\, (x=a)$
$RHD \, at\, x=$
$=\underset{h \rightarrow 0}{\lim}\dfrac{f(0+h)-f(0)}{h}$
$=\underset{h \rightarrow 0}{\lim}\dfrac{f(h)-f(0)}{h}$
$=\underset{h \rightarrow 0}{\lim}\dfrac{h^2\sin \left(\dfrac{1}{h}\right)-0}{h}$
$=\underset{h \rightarrow 0}{\lim} h \sin \left(\dfrac{1}{h}\right)=0\times (value \, between\, -1\&1)$
$=0$
Now 
LHD at $x=0$.
$=\underset{h \rightarrow 0}{\lim}\dfrac{f(0-h)-f(0)}{-h}$
$=\underset{h \rightarrow 0}{\lim}\dfrac{f(-h)-f(0)}{-h}$
$\underset{h \rightarrow 0}{\lim} \dfrac{(-h)^2\sin \left(-\dfrac{1}{h}\right)-0}{-h}$
$\underset{h \rightarrow 0}{\lim} -h \sin \left(-\dfrac{1}{h}\right)=\underset{h \rightarrow 0}{\lim} h \sin \dfrac{1}{h}$
$=0\times [-1,1]$
$=0$
Here $\because LHD =RHD =0$ at $x=0$
Hence $f$ is derivable at $x=0$
Important Concept : Left Hand derivative $ (LHD)=\underset{h \rightarrow 0}{\lim} \dfrac{f(a-h)-f(a)}{-h}$
$RHD$ at $(x=a)=\underset{h \rightarrow 0}{\lim}\dfrac{f(a+h)-f(a)}{h}$

Consider the following statements:
$1.$ Derivative of $f(x)$ may not exist at some point.
$2.$ Derivative of $f(x)$ may exist finitely at some point.
$3.$ Derivative of $f(x)$ may be infinite (geometrically) at some point.
Which of the above statements are correct?

  1. $1$ and $2$ only

  2. $2$ and $3$ only

  3. $1$ and $3$ only

  4. $1, 2$ and $3$


Correct Option: D
Explanation:

Lets check each statement one by one

1. This statement is true. Take example $y=|x|$ derivative does not exist at $x=0$
2. This statement is true. Derivative may  be finite may be not. Take example of $y=\tan x$
3. Derivative of a function can be infinite(undefined) 
Hence, all three statements are true.

$f(x)= \left\{\begin{matrix}x^2+3x+a & \text{for}\, x \leq 1 \\ bx+2 & \text{for}\, x > 1 \end{matrix}\right.$ 
is everywhere differentiable. Then value of constant $b$ is
  1. $5$

  2. $3$

  3. $\dfrac{1}{5}$

  4. None of these


Correct Option: A
Explanation:

Given it is differentiable everywhere,
Therefore, 

$f'(x)=\begin{cases} 2x+3 &, x \leq 1 \ b &, x>1 \end{cases}$

At $ x=1, f'(1)=2(1)+3=5$

When $x>1$

As $f$ is differentiable at every point, both left-hand and right-hand derivatives should be equal.

$\therefore f'(1)=b$

$\Rightarrow 5=b$

Hence, $b=5$.

A function is defined in $(0, \infty)$ by
$f(x) = \left{\begin{matrix}1 - x^{2} & for & 0 < x  \leq 1\ \ln\ x & for & 1 < x \leq 2\ \ln\ 2 - 1 + 0.5x & for & 2 < x < \infty\end{matrix}\right.$
Which one of the following is correct in respect of the derivative of the function, i.e., $f'(x)$?

  1. $f'(x) = 2x$  for  $0 < x \leq 1$

  2. $f'(x) = -2x$  for  $0 < x \leq 1$

  3. $f'(x) = -2x$  for  $0 < x < 1$

  4. $f'(x) = 0$  for  $0 < x < \infty$


Correct Option: B
Explanation:
$f(x)$ is continuous at $x=1$ and at $x=2$.
Differentiating w.r.t $x$
$f'(x)=\left\lbrace\begin{matrix}-2x & \text{for} & 0<x\leq 1 \\ \dfrac{1}{x} & \text{for} & 1<x\leq2 \\ 0.5 & \text{for} & 2<x<\infty\end{matrix}\right\rbrace$

$f(x)= \left\{\begin{matrix}x^2+3x+a & \text{for}\, x \leq 1 \\ bx+2 & \text{for}\, x > 1 \end{matrix}\right.$
is everywhere differentiable. Then value of constant $a$ is
  1. $3$

  2. $\dfrac{1}{3}$

  3. $5$

  4. None of these


Correct Option: A
Explanation:

Given :


$f\left( x \right) =\begin{cases} { x }^{ 2 }+3x+a\quad \quad for\quad x\le 1\quad  \ bx+2\quad \quad \quad \quad \quad for\quad x>1 \end{cases}$

$f\left( x \right) =\begin{cases} { x }^{ 2 }+3x+a\quad \quad ;\quad x\le 1\quad  \ bx+2\quad \quad \quad \quad \quad ;\quad x>1 \end{cases}$

Since $\ { x }^{ 2 }+3x+a$ quadratic and $bx+2$ is linear equation.Therefore the equations are continous.
Hence,we will check differetiability of this equation as $x=1$

$f\left( { 1 }^{ - } \right) =f\left( { 1 }^{ + } \right) $ [since the equation is continous]
$1+3+a=b+2$
$a+4=b+2$
$\Rightarrow a-b=-2\rightarrow (1)$

$f^{ 1 }\left( x \right) =\begin{cases} 2x+3\quad \quad for\quad x\le 1\quad  \ b\quad \quad \quad \quad \quad for\quad x>1 \end{cases}$

$f^{ 1 }\left( { 1 }^{ - } \right) =f^{ 1 }\left( { 1 }^{ + } \right) $ [since $f(x)$ is differentiable at each point of $x$]
$2+3=b$
$b=5$
Substitute b=5 in equation (1)
$a-b=-2$
$a-5=-2$
$a=3$
Hence the correct answer is $3$.


 lf $\mathrm{f}(\mathrm{x})=\left{\begin{array}{l}1, \mathrm{x}<0\1+ \mathrm{s}\mathrm{i}\mathrm{n}\mathrm{x}, 0\leq \mathrm{x}</\pi _{2} \end{array}\right.$, then derivative of f(x) at$\mathrm{x}=0$

  1. is equal to 1

  2. is equal to 0

  3. is equal to -1

  4. does not exist


Correct Option: D
Explanation:

LHD at x=0

=${ \left[ \frac { d }{ dx } 1 \right]  } _{ x=0 }=0$
RHD at x=0
=${ \left[ \frac { d }{ dx } 1+\sin { x }  \right]  } _{ x=0 }=cos0=1$
hence $f'$ doesn't exist

If $f(x)=(4+x)^{n}$,$n \epsilon N$ and $f^{r}(0)$ represents the $r^{th}$ derivative of f(x) at x = 0, then the value of $\sum _{r=0}^{\infty}\frac{(f^{r}(0))}{r!}$ is equal to

  1. $2^{n}$

  2. $e^{n}$

  3. $5^{n}$

  4. $4^{n}$


Correct Option: C
Explanation:

$f'(x)=n(4+x)^{n-1},f''=n(n-1).(4+x)^{n-2}$
If we keep on differentiating, we get
$f^{r}=n(n-1)....(n-r+1).(4+x)^{n-r},r\leq 4$
$\Rightarrow f^{r}(0)=\frac{n!}{(n-r)!}.4^{n-r},r\leq n$
and $f^{r}(0)=0 for r>n$
$\sum _{r=0}^{\infty}\frac{(f^{r}(0))}{r!}$=$5^{n}$

Let $f(x)=\begin{cases}\begin{matrix} 1 & \forall &  x<0 \ 1+\sin x & \forall & 0\leq x\leq \dfrac{\pi}2\end{matrix}\end{cases}$ then what is the value of $f'(x)$ at $x=0?$

  1. $1$

  2. $-1$

  3. $\infty$

  4. Does not exist


Correct Option: D
Explanation:

For $x<0$ , $f(x)=1$

$\Rightarrow f^{ 1 }\left( 0^{-}\right) =0$
For $x\ge 0$ , $f(x)=1+sinx$
$\Rightarrow f^{ 1 }\left( 0^{+} \right) = cos(0)=1 $
Therefore $f^{ 1 }\left( 0^{-} \right) \neq f^{ 1 }\left( 0^{+} \right)$  
So $f^{ 1 }\left( x \right) $ at $x=0$ does not exist
Therefore the correct option is $D$

The second order differential equation is :

  1. ${ y' }^{ 2 }+x={ y }^{ 2 }$

  2. $y'+y''+y=\sin { x } $

  3. $y'''+y''+y=0$

  4. $y'=y$


Correct Option: B
Explanation:

We know that, the order of the differential equation is the order of highest derivative.
So, equation $y'+y''+y=\sin { x } $ is the second order differential equation.

$f\left( x \right) = \left| {x - 1} \right| + \left| {x + 2} \right| + \left| {x - 3} \right|$ is not differentiable at

  1. 2 points

  2. 3 points

  3. 4 points

  4. 1 point


Correct Option: B
Explanation:

Given $f(x)=\left | x-1 \right |+\left | x+2 \right |+\left | x-3 \right |$

$\therefore f(x)=(1-x)+-(x-2)+(3-x)$   For $x<-2$
  $\quad \quad =2-3x$    For $x<-2$
$f(x)=(1-x)+(x+2)+(3-x)$   For $-2\leq x< 1$
   $\quad \quad=6-x$       For $-2\leq x< 1$
$f(x)=x-1+x+2+3-x$ For $1\leq x< 3$
   $\quad \quad =4+x$    For $1\leq x< 3$
$f(x)=x-1+x+2+x-3$
   $\quad \quad =3x-2$ For $x\geq 3$

$\therefore f(x) =\left \{ 2-3x \right.\quad x<-2$
                  $ \left \{ 6-x \right.\quad -2\leq x< 1$
                  $ \left \{ 4+x \right.\quad 1\leq x< 3 $
                  $ \left \{ 3x-2 \right.\quad x\geq 3$

$ {f}'(x)=\left { -3 \right. \quad x<-2 $
               $  \left { -1 \right. \quad -2\leq x< 1 $
               $  \left { 1 \right. \quad \ 1\leq x< 3 $
               $   \left { 3 \right.\quad x\geq 3$
   $\therefore f(x)$ is not differentiable at x=-2,1,3

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