Recurrence Relations

Description: This quiz covers fundamental concepts and techniques related to recurrence relations, a core topic in combinatorics and discrete mathematics.
Number of Questions: 14
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What is the general form of a linear homogeneous recurrence relation of order k?

  1. a_n = c_1 * a_{n-1} + c_2 * a_{n-2} + ... + c_k * a_{n-k}

  2. a_n = c_1 * a_{n-1} + c_2 * a_{n-2} + ... + c_k * a_{n+k}

  3. a_n = c_1 * a_{n+1} + c_2 * a_{n+2} + ... + c_k * a_{n+k}

  4. a_n = c_1 * a_{n-1} + c_2 * a_{n-2} + ... + c_k * a_{n-1}


Correct Option: A
Explanation:

A linear homogeneous recurrence relation of order k has the form a_n = c_1 * a_{n-1} + c_2 * a_{n-2} + ... + c_k * a_{n-k}, where c_1, c_2, ..., c_k are constants and a_0, a_1, ..., a_{k-1} are the initial conditions.

Which of the following is a characteristic equation for the recurrence relation a_n = 3 * a_{n-1} - 2 * a_{n-2}?

  1. r^2 - 3 * r + 2 = 0

  2. r^2 + 3 * r + 2 = 0

  3. r^2 - 3 * r - 2 = 0

  4. r^2 + 3 * r - 2 = 0


Correct Option: A
Explanation:

The characteristic equation for the recurrence relation a_n = 3 * a_{n-1} - 2 * a_{n-2} is r^2 - 3 * r + 2 = 0, which is obtained by substituting a_n = r^n into the recurrence relation.

What is the general solution to the recurrence relation a_n = 3 * a_{n-1} - 2 * a_{n-2} with initial conditions a_0 = 1 and a_1 = 2?

  1. a_n = 2^n + 1

  2. a_n = 2^n - 1

  3. a_n = 3^n + 1

  4. a_n = 3^n - 1


Correct Option: A
Explanation:

The general solution to the recurrence relation a_n = 3 * a_{n-1} - 2 * a_{n-2} with initial conditions a_0 = 1 and a_1 = 2 is a_n = 2^n + 1, which can be found using the method of undetermined coefficients.

Which of the following is a recurrence relation for the Fibonacci sequence?

  1. F_n = F_{n-1} + F_{n-2}

  2. F_n = F_{n-1} - F_{n-2}

  3. F_n = 2 * F_{n-1} - F_{n-2}

  4. F_n = 2 * F_{n-1} + F_{n-2}


Correct Option: A
Explanation:

The Fibonacci sequence is defined by the recurrence relation F_n = F_{n-1} + F_{n-2}, with initial conditions F_0 = 0 and F_1 = 1.

What is the generating function for the sequence {1, 2, 4, 8, 16, ...}?

  1. G(x) = 1 / (1 - 2 * x)

  2. G(x) = 1 / (1 + 2 * x)

  3. G(x) = 1 / (1 - 4 * x)

  4. G(x) = 1 / (1 + 4 * x)


Correct Option: A
Explanation:

The generating function for the sequence {1, 2, 4, 8, 16, ...} is G(x) = 1 / (1 - 2 * x), which can be obtained using the formula for the generating function of a geometric sequence.

Which of the following is a recurrence relation for the number of ways to climb n stairs, if you can take either one step or two steps at a time?

  1. f(n) = f(n-1) + f(n-2)

  2. f(n) = f(n-1) - f(n-2)

  3. f(n) = 2 * f(n-1) - f(n-2)

  4. f(n) = 2 * f(n-1) + f(n-2)


Correct Option: A
Explanation:

The number of ways to climb n stairs, if you can take either one step or two steps at a time, is given by the recurrence relation f(n) = f(n-1) + f(n-2), with initial conditions f(0) = 1 and f(1) = 1.

What is the asymptotic behavior of the solution to the recurrence relation a_n = 2 * a_{n-1} - 3 * a_{n-2} as n approaches infinity?

  1. a_n ~ 2^n

  2. a_n ~ 3^n

  3. a_n ~ (-2)^n

  4. a_n ~ (-3)^n


Correct Option: A
Explanation:

The asymptotic behavior of the solution to the recurrence relation a_n = 2 * a_{n-1} - 3 * a_{n-2} as n approaches infinity is a_n ~ 2^n, which can be determined by analyzing the characteristic equation of the recurrence relation.

Which of the following is a recurrence relation for the number of ways to partition a set of n elements into k non-empty subsets?

  1. S(n, k) = S(n-1, k) + S(n-1, k-1)

  2. S(n, k) = S(n-1, k) - S(n-1, k-1)

  3. S(n, k) = 2 * S(n-1, k) - S(n-1, k-1)

  4. S(n, k) = 2 * S(n-1, k) + S(n-1, k-1)


Correct Option: A
Explanation:

The number of ways to partition a set of n elements into k non-empty subsets is given by the recurrence relation S(n, k) = S(n-1, k) + S(n-1, k-1), with initial conditions S(n, 0) = 0 and S(0, k) = 0.

What is the generating function for the sequence {1, 1, 2, 3, 5, 8, 13, ...}, where each term is the sum of the two previous terms?

  1. G(x) = 1 / (1 - x - x^2)

  2. G(x) = 1 / (1 + x + x^2)

  3. G(x) = 1 / (1 - x + x^2)

  4. G(x) = 1 / (1 + x - x^2)


Correct Option: A
Explanation:

The generating function for the sequence {1, 1, 2, 3, 5, 8, 13, ...} is G(x) = 1 / (1 - x - x^2), which can be obtained using the formula for the generating function of a Fibonacci-like sequence.

Which of the following is a recurrence relation for the number of ways to make change for n cents using coins of denominations 1, 5, and 10 cents?

  1. C(n) = C(n-1) + C(n-5) + C(n-10)

  2. C(n) = C(n-1) - C(n-5) - C(n-10)

  3. C(n) = 2 * C(n-1) - C(n-5) + C(n-10)

  4. C(n) = 2 * C(n-1) + C(n-5) - C(n-10)


Correct Option: A
Explanation:

The number of ways to make change for n cents using coins of denominations 1, 5, and 10 cents is given by the recurrence relation C(n) = C(n-1) + C(n-5) + C(n-10), with initial conditions C(0) = 1 and C(i) = 0 for i < 0.

What is the asymptotic behavior of the solution to the recurrence relation a_n = 3 * a_{n-1} - 2 * a_{n-2} as n approaches infinity?

  1. a_n ~ 3^n

  2. a_n ~ 2^n

  3. a_n ~ (-3)^n

  4. a_n ~ (-2)^n


Correct Option: A
Explanation:

The asymptotic behavior of the solution to the recurrence relation a_n = 3 * a_{n-1} - 2 * a_{n-2} as n approaches infinity is a_n ~ 3^n, which can be determined by analyzing the characteristic equation of the recurrence relation.

Which of the following is a recurrence relation for the number of ways to arrange n distinct objects in a row?

  1. P(n) = P(n-1) + 1

  2. P(n) = P(n-1) - 1

  3. P(n) = 2 * P(n-1) + 1

  4. P(n) = 2 * P(n-1) - 1


Correct Option: A
Explanation:

The number of ways to arrange n distinct objects in a row is given by the recurrence relation P(n) = P(n-1) + 1, with initial condition P(0) = 1.

What is the generating function for the sequence {1, 4, 9, 16, 25, ...}?

  1. G(x) = 1 / (1 - 4 * x)

  2. G(x) = 1 / (1 + 4 * x)

  3. G(x) = 1 / (1 - 2 * x)

  4. G(x) = 1 / (1 + 2 * x)


Correct Option: A
Explanation:

The generating function for the sequence {1, 4, 9, 16, 25, ...} is G(x) = 1 / (1 - 4 * x), which can be obtained using the formula for the generating function of a quadratic sequence.

Which of the following is a recurrence relation for the number of ways to color n balls using k colors, if each ball can be colored with any of the k colors?

  1. C(n, k) = C(n-1, k) + C(n-1, k-1)

  2. C(n, k) = C(n-1, k) - C(n-1, k-1)

  3. C(n, k) = 2 * C(n-1, k) + C(n-1, k-1)

  4. C(n, k) = 2 * C(n-1, k) - C(n-1, k-1)


Correct Option: A
Explanation:

The number of ways to color n balls using k colors, if each ball can be colored with any of the k colors, is given by the recurrence relation C(n, k) = C(n-1, k) + C(n-1, k-1), with initial conditions C(0, k) = 0 and C(n, 0) = 0.

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