Math Problem Statement

Find the 7th term of the geometric sequence 9, 3, 1, .

Solution

To find the 7th term of a geometric sequence, we use the formula for the nnth term of a geometric sequence:

an=a1rn1a_n = a_1 \cdot r^{n-1}

where:

  • a1a_1 is the first term,
  • rr is the common ratio,
  • nn is the term number.

From the sequence given (9, 3, 1, ...):

  • The first term a1=9a_1 = 9,
  • The common ratio r=39=13r = \frac{3}{9} = \frac{1}{3}.

Now, using the formula to find the 7th term (n=7n = 7):

a7=9(13)71=9(13)6a_7 = 9 \cdot \left(\frac{1}{3}\right)^{7-1} = 9 \cdot \left(\frac{1}{3}\right)^6

a7=91729=9729=181a_7 = 9 \cdot \frac{1}{729} = \frac{9}{729} = \frac{1}{81}

Thus, the 7th term of the geometric sequence is 181\frac{1}{81}.

Would you like further details or have any 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 happens if the common ratio is negative in a geometric sequence?
  3. How do you determine if a sequence is arithmetic or geometric?
  4. How do you find the general formula for any term in a geometric sequence?
  5. What is the difference between finite and infinite geometric series?

Tip: Always double-check the common ratio before applying the geometric sequence formula.

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Math Problem Analysis

Mathematical Concepts

Geometric Sequences
Ratios
Exponents

Formulas

a_n = a_1 * r^(n-1)

Theorems

Geometric Sequence Formula

Suitable Grade Level

Grades 8-10