Math Problem Statement

Which recursive formula can be used to define this sequence for n>1? 2, 6, 18, 54, 162, 486,

Solution

To determine the recursive formula for the given sequence 2,6,18,54,162,4862, 6, 18, 54, 162, 486, let's observe the pattern:

Step 1: Analyze the pattern

The ratio between consecutive terms is constant: 62=3,186=3,5418=3,16254=3,486162=3\frac{6}{2} = 3, \quad \frac{18}{6} = 3, \quad \frac{54}{18} = 3, \quad \frac{162}{54} = 3, \quad \frac{486}{162} = 3

This indicates that the sequence is geometric with a common ratio of 3.

Step 2: Define the recursive formula

The first term of the sequence is: a1=2a_1 = 2 For n>1n > 1, each term is obtained by multiplying the previous term by 3: an=3an1,for n>1a_n = 3 \cdot a_{n-1}, \quad \text{for } n > 1

Final Recursive Formula:

a1=2,an=3an1 for n>1a_1 = 2, \quad a_n = 3 \cdot a_{n-1} \text{ for } n > 1


Would you like further details on geometric sequences or examples? Here are some related questions to deepen understanding:

  1. How do you derive the general (explicit) formula for a geometric sequence?
  2. What is the sum of the first nn terms of a geometric sequence?
  3. How can you identify a recursive formula for a sequence with varying patterns?
  4. Can this recursive formula be modified for sequences starting with different values?
  5. What are practical applications of geometric sequences?

Tip: When working with sequences, always check for consistency in the differences or ratios between terms to identify patterns!

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Math Problem Analysis

Mathematical Concepts

Sequences
Geometric Sequences
Recursion

Formulas

Recursive formula for geometric sequences: a_n = r * a_(n-1)

Theorems

Geometric sequence properties

Suitable Grade Level

Grades 8-10