Math Problem Statement

find the sum of the first 10 term of the geometric sequence 8,4,2

Solution

The sequence given is 8,4,2,8, 4, 2, \dots, which is a geometric sequence.

Step 1: Identify the first term aa and the common ratio rr

  • First term a=8a = 8
  • The common ratio r=48=12r = \frac{4}{8} = \frac{1}{2}

Step 2: Use the formula for the sum of the first nn terms of a geometric sequence:

Sn=a(1rn)1rS_n = \frac{a(1 - r^n)}{1 - r} Where:

  • SnS_n is the sum of the first nn terms,
  • aa is the first term,
  • rr is the common ratio,
  • nn is the number of terms.

For the first 10 terms, we have:

  • a=8a = 8,
  • r=12r = \frac{1}{2},
  • n=10n = 10.

Step 3: Substitute the values into the formula:

S10=8(1(12)10)112S_{10} = \frac{8(1 - \left(\frac{1}{2}\right)^{10})}{1 - \frac{1}{2}}

Step 4: Simplify the expression:

S10=8(1(11024))12=8(10.0009765625)12=8×0.999023437512=16×0.9990234375S_{10} = \frac{8(1 - \left(\frac{1}{1024}\right))}{\frac{1}{2}} = \frac{8(1 - 0.0009765625)}{\frac{1}{2}} = \frac{8 \times 0.9990234375}{\frac{1}{2}} = 16 \times 0.9990234375

S1015.984375S_{10} \approx 15.984375

Thus, the sum of the first 10 terms of the geometric sequence is approximately 15.98.

Would you like more details or have any questions?

Here are 5 related questions to further explore the concept:

  1. What happens to the sum if the common ratio is greater than 1?
  2. How do you find the sum of an infinite geometric sequence?
  3. What is the sum of the first 5 terms of this sequence?
  4. How can you determine whether a sequence is geometric?
  5. What is the formula for the nth term of a geometric sequence?

Tip: The sum of an infinite geometric series only converges if the absolute value of the common ratio is less than 1.

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Math Problem Analysis

Mathematical Concepts

Geometric Sequence
Summation

Formulas

Sum of geometric sequence formula: S_n = a(1 - r^n) / (1 - r)

Theorems

Geometric Series Theorem

Suitable Grade Level

Grades 8-10