Math Problem Statement

If f(1) = 10 and f(n) = -2f(n-1), then find the value of f(5).

Solution

We are tasked with finding f(5)f(5), given:

  1. f(1)=10f(1) = 10
  2. f(n)=2f(n1)f(n) = -2f(n-1) for n2n \geq 2

Step-by-step Solution:

Using the recurrence relation f(n)=2f(n1)f(n) = -2f(n-1), we compute the values of f(2)f(2), f(3)f(3), f(4)f(4), and f(5)f(5):

  1. Base case: f(1)=10f(1) = 10
  2. f(2)=2f(1)=210=20f(2) = -2f(1) = -2 \cdot 10 = -20
  3. f(3)=2f(2)=2(20)=40f(3) = -2f(2) = -2 \cdot (-20) = 40
  4. f(4)=2f(3)=240=80f(4) = -2f(3) = -2 \cdot 40 = -80
  5. f(5)=2f(4)=2(80)=160f(5) = -2f(4) = -2 \cdot (-80) = 160

Final Answer:

f(5)=160f(5) = 160

Let me know if you'd like further clarification or additional details!


Follow-up Questions:

  1. How does a recurrence relation define a sequence?
  2. What happens if the initial value f(1)f(1) changes?
  3. Can this recurrence relation be expressed explicitly as a closed-form formula?
  4. What are some examples of recurrence relations in real-world applications?
  5. How do negative coefficients affect the behavior of sequences?

Tip: When solving recurrence relations, always compute several terms to ensure your understanding of the sequence's behavior.

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Math Problem Analysis

Mathematical Concepts

Recurrence Relations
Arithmetic Sequences
Algebra

Formulas

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

Theorems

None directly; uses iterative computation

Suitable Grade Level

Grades 9-12