Find the sum of each infinite geometric series. ∑i=1∞8(−0.3)i−1\sum_{i=1}^{\infty} $$8(-0.3)^{i-1}$$

Ch. 8 - Sequences, Induction, and Probability

Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook

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Blitzer 8th Edition

Ch. 8 - Sequences, Induction, and Probability

Problem 43

Chapter 9, Problem 43

Find the sum of each infinite geometric series. $\sum_{i = 1}^{\infty} 8 (- 0.3)^{i - 1}$

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Identify the first term $ a $ of the infinite geometric series. Since the series is given by $ \sum_{i=1}^{\infty} 8(-0.3)^{i-1} $, the first term corresponds to $ i=1 $, so $ a = 8(-0.3)^{0} = 8 $.

Determine the common ratio $ r $ of the geometric series. The common ratio is the factor by which each term is multiplied to get the next term, which is $ r = -0.3 $.

Check the condition for the sum of an infinite geometric series to exist. The sum converges only if the absolute value of the common ratio is less than 1, i.e., $ |r| < 1 $. Since $ |-0.3| = 0.3 < 1 $, the series converges.

Use the formula for the sum of an infinite geometric series: \[ S = \frac{a}{1 - r} \]. Substitute the values of $ a = 8 $ and $ r = -0.3 $ into the formula.

Simplify the expression $ \frac{8}{1 - (-0.3)} $ to find the sum of the series. This will give you the sum without calculating the final numeric value.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Infinite Geometric Series

An infinite geometric series is the sum of infinitely many terms where each term is found by multiplying the previous term by a constant ratio. It converges only if the absolute value of the common ratio is less than 1, allowing the sum to approach a finite value.

Common Ratio

The common ratio in a geometric series is the factor by which each term is multiplied to get the next term. It is crucial for determining whether the series converges and for calculating the sum of the series when |r| < 1.

Sum Formula for Infinite Geometric Series

The sum of an infinite geometric series with first term a and common ratio r (where |r| < 1) is given by S = a / (1 - r). This formula allows us to find the finite sum of the series when it converges.

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