Math Problem Statement

Ak- 7a(k-1) + 10 a(k-2) = 0 solve recurrence relation

Solution

The given recurrence relation is:

Ak7Ak1+10Ak2=0A_k - 7A_{k-1} + 10A_{k-2} = 0

This is a second-order linear homogeneous recurrence relation with constant coefficients. To solve this, we follow these steps:

Step 1: Set up the characteristic equation.

Assume a solution of the form Ak=rkA_k = r^k, where rr is some constant. Substituting this into the recurrence relation:

rk7rk1+10rk2=0r^k - 7r^{k-1} + 10r^{k-2} = 0

Dividing through by rk2r^{k-2} (assuming r0r \neq 0):

r27r+10=0r^2 - 7r + 10 = 0

Step 2: Solve the characteristic equation.

The characteristic equation is:

r27r+10=0r^2 - 7r + 10 = 0

Solve this quadratic equation using the quadratic formula:

r=(7)±(7)24(1)(10)2(1)r = \frac{-(-7) \pm \sqrt{(-7)^2 - 4(1)(10)}}{2(1)} r=7±49402r = \frac{7 \pm \sqrt{49 - 40}}{2} r=7±92r = \frac{7 \pm \sqrt{9}}{2} r=7±32r = \frac{7 \pm 3}{2}

So, the roots are:

r1=7+32=5,r2=732=2r_1 = \frac{7 + 3}{2} = 5, \quad r_2 = \frac{7 - 3}{2} = 2

Step 3: General solution.

Since the characteristic equation has two distinct real roots r1=5r_1 = 5 and r2=2r_2 = 2, the general solution to the recurrence relation is:

Ak=C15k+C22kA_k = C_1 \cdot 5^k + C_2 \cdot 2^k

where C1C_1 and C2C_2 are constants that can be determined from initial conditions.

If initial conditions are provided (such as values of A0A_0 and A1A_1), we can solve for C1C_1 and C2C_2.

Would you like to provide initial conditions, or do you need further details?


Here are 5 related questions:

  1. How do initial conditions affect the solution of a recurrence relation?
  2. What happens if the characteristic equation has repeated roots?
  3. Can this method be applied to non-homogeneous recurrence relations?
  4. How does solving a recurrence relation differ from solving a differential equation?
  5. What are some common applications of recurrence relations in computer science?

Tip: When solving recurrence relations, always check for distinct, repeated, or complex roots in the characteristic equation.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Recurrence Relations
Algebra
Characteristic Equation

Formulas

A_k = r^k
Quadratic equation r^2 - 7r + 10 = 0
General solution: A_k = C_1 * 5^k + C_2 * 2^k

Theorems

Quadratic Formula
Solution of Homogeneous Recurrence Relations

Suitable Grade Level

Grades 11-12 and Early College