Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 4 - Exponential and Logarithmic Functions - Section 4.5 Properties of Logarithms - 4.5 Assess Your Understanding - Page 331: 62

Answer

$\log \left(\dfrac{x+2}{x+1} \right)$

Work Step by Step

Recall: $\log_a M^r = r \log_a M$ Using the rule above gives: $2 \log (x+1) = \log (x+1)^2$ So the given expression is equivalent to: $\log (x^2+3x+2) - \log(x+1)^2$ With $\log_a\left(\dfrac{M}{N}\right) = \log_a M-\log_a N$, then the expression above is equivalent to: $\log \left(\dfrac{x^2+3x+2}{(x+1)^2} \right)$ Note that $ x^2+3x+2=(x+2)(x+1)$. Hence, the expression above simplifies to: $\require{cancel} \log \left(\dfrac{(x+2)(x+1)}{(x+1)^2} \right) \\\\ \log \left(\dfrac{(x+2)\cancel{(x+1)}}{(x+1)^\cancel{2}} \right) \\\\ = \log \left(\dfrac{x+2}{x+1} \right)$ Therefore, $\log (x^2+3x+2) - 2 \log (x+1) = \boxed{\log \left(\dfrac{x+2}{x+1} \right)}$
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