Math Problem Statement

Write the first five terms of the sequence. a1=−1 , an=(−4)n−1an−1−3 for n≥2

Solution

To find the first five terms of the sequence where:

a1=1a_1 = -1 an=(4)n1an13, for n2,a_n = (-4)^{n-1} a_{n-1} - 3, \text{ for } n \geq 2,

we calculate each term step by step:

Step 1: Calculate a2a_2

a2=(4)21a13a_2 = (-4)^{2-1} a_1 - 3 a2=(4)1(1)3a_2 = (-4)^1 \cdot (-1) - 3 a2=43=1a_2 = 4 - 3 = 1

Step 2: Calculate a3a_3

a3=(4)31a23a_3 = (-4)^{3-1} a_2 - 3 a3=(4)213a_3 = (-4)^2 \cdot 1 - 3 a3=163=13a_3 = 16 - 3 = 13

Step 3: Calculate a4a_4

a4=(4)41a33a_4 = (-4)^{4-1} a_3 - 3 a4=(4)3133a_4 = (-4)^3 \cdot 13 - 3 a4=64133=8323=835a_4 = -64 \cdot 13 - 3 = -832 - 3 = -835

Step 4: Calculate a5a_5

a5=(4)51a43a_5 = (-4)^{5-1} a_4 - 3 a5=(4)4(835)3a_5 = (-4)^4 \cdot (-835) - 3 a5=256(835)3=2137603=213763a_5 = 256 \cdot (-835) - 3 = -213760 - 3 = -213763

First Five Terms

The first five terms of the sequence are: a1=1,  a2=1,  a3=13,  a4=835,  a5=213763a_1 = -1, \; a_2 = 1, \; a_3 = 13, \; a_4 = -835, \; a_5 = -213763


Do you want a detailed explanation of how each term was calculated or have any further questions?

Five Related Questions:

  1. What happens to the sequence for larger values of nn?
  2. How does the term (4)n1(-4)^{n-1} affect the growth of the sequence?
  3. Can we derive a closed-form expression for this sequence?
  4. What is the nature of the sequence (divergent, bounded, etc.)?
  5. How does the sequence change if a1a_1 is a different value?

Tip:

When working with recursive sequences, always compute a few terms explicitly to understand the behavior before trying to generalize.

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Math Problem Analysis

Mathematical Concepts

Sequences
Recursive Formulas
Exponential Growth

Formulas

a1 = -1
an = (−4)^(n−1)an−1 − 3 for n ≥ 2

Theorems

Recursive sequence computation

Suitable Grade Level

Grades 10-12