Math Problem Statement

what is the 8th term of the geometric sequence 6,18,54,162

Solution

To find the 8th term of a geometric sequence, we use the formula for the nn-th term of a geometric sequence:

an=a1r(n1)a_n = a_1 \cdot r^{(n-1)}

where:

  • ana_n is the nn-th term.
  • a1a_1 is the first term.
  • rr is the common ratio.
  • nn is the term number.

For the given sequence 6,18,54,162,6, 18, 54, 162, \ldots:

  1. The first term a1=6a_1 = 6.
  2. The common ratio rr can be found by dividing the second term by the first term:

r=186=3r = \frac{18}{6} = 3

Now, we need to find the 8th term (a8a_8):

a8=63(81)a_8 = 6 \cdot 3^{(8-1)}

Calculating 373^{7}:

37=21873^7 = 2187

Now, compute a8a_8:

a8=62187=13122a_8 = 6 \cdot 2187 = 13122

Answer:

The 8th term of the geometric sequence is 13,122.

Would you like a detailed explanation of how I calculated this or have any other questions?

Here are 5 related questions to explore further:

  1. How do you find the sum of the first nn terms of a geometric sequence?
  2. What is the 10th term of a geometric sequence where the first term is 5 and the common ratio is 2?
  3. How do you determine if a sequence is geometric?
  4. Can you derive the formula for the nn-th term of a geometric sequence?
  5. How would you find the common ratio if only the 3rd and 5th terms of a geometric sequence are given?

Tip: In geometric sequences, the common ratio remains constant throughout the sequence.

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Math Problem Analysis

Mathematical Concepts

Geometric Sequences
Exponential Growth

Formulas

a_n = a_1 * r^(n-1)

Theorems

Geometric Sequence Formula

Suitable Grade Level

Grades 9-12