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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 10.7.5

Simplify k! / (k + 2)! for any integer k ≥ 0.

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Recall the definition of factorial: for any integer n ≥ 0, n! = n × (n - 1) × (n - 2) × ... × 1, and 0! = 1 by convention.
Express the denominator (k + 2)! in terms of k!: write (k + 2)! as (k + 2) × (k + 1) × k!.
Rewrite the original expression \( \frac{k!}{(k + 2)!} \) by substituting the expanded form of (k + 2)!: \( \frac{k!}{(k + 2) \times (k + 1) \times k!} \).
Cancel the common factor k! in numerator and denominator, simplifying the expression to \( \frac{1}{(k + 2) \times (k + 1)} \).
Conclude that the simplified form of \( \frac{k!}{(k + 2)!} \) is \( \frac{1}{(k + 2)(k + 1)} \) for any integer k ≥ 0.

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Factorial Definition

The factorial of a non-negative integer n, denoted n!, is the product of all positive integers from 1 up to n. By definition, 0! = 1. Understanding factorials is essential for simplifying expressions involving factorial terms.
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Factorial Expansion and Cancellation

To simplify ratios of factorials like k! / (k + 2)!, expand the larger factorial to reveal common factors. For example, (k + 2)! = (k + 2)(k + 1)k!, allowing cancellation of k! in numerator and denominator.
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Simplification of Rational Expressions

After canceling common factorial terms, simplify the remaining expression by performing arithmetic operations. This often reduces complex factorial ratios to simpler algebraic fractions or products.
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