Skip to main content
Ch. 10 - Sequences and Infinite Series
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Capitolo 10, Problema 10.R.3

Geometric sums
Evaluate the geometric sums
∑ (from k = 0 to 9) (0.2)ᵏand∑ (from k = 2 to 9) (0.2)ᵏ.

Guida verificata passo dopo passo
1
Recognize that both sums are geometric series where each term is of the form \(r^k\) with common ratio \(r = 0.2\).
Recall the formula for the sum of the first \(n+1\) terms of a geometric series starting at \(k=0\): \(S = \frac{1 - r^{n+1}}{1 - r}\).
For the first sum \(\sum_{k=0}^{9} (0.2)^k\), identify \(n=9\) and apply the formula: \(S_1 = \frac{1 - (0.2)^{10}}{1 - 0.2}\).
For the second sum \(\sum_{k=2}^{9} (0.2)^k\), express it as the difference between the sum from \(k=0\) to \(9\) and the sum from \(k=0\) to \(1\): \(S_2 = \sum_{k=0}^{9} (0.2)^k - \sum_{k=0}^{1} (0.2)^k\).
Calculate \(\sum_{k=0}^{1} (0.2)^k\) using the geometric sum formula with \(n=1\): \(S_{0\text{ to }1} = \frac{1 - (0.2)^2}{1 - 0.2}\), then subtract this from \(S_1\) to find \(S_2\).

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.
Durata del video:
3m

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Geometric Series

A geometric series is the sum of terms where each term is found by multiplying the previous term by a constant ratio. It has the form ∑ ar^k, where a is the first term and r is the common ratio. Understanding this structure is essential for evaluating sums like those given.
Video consigliato:
Percorso guidato
06:00
Geometric Series

Formula for the Sum of a Finite Geometric Series

The sum of the first n+1 terms of a geometric series is given by S = a(1 - r^(n+1)) / (1 - r), where a is the first term and r is the common ratio (r ≠ 1). This formula allows quick calculation of sums without adding each term individually.
Video consigliato:
Percorso guidato
06:00
Geometric Series

Index Shifting in Summations

When the summation index does not start at zero, it is often helpful to rewrite the sum by shifting the index to start at zero. This simplifies applying the geometric series formula by adjusting the first term and the number of terms accordingly.
Video consigliato: