College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 5 - Summary, Review, and Test - Cumulative Review Exercises (Chapters 1-5) - Page 587: 17

Answer

$x=2$

Work Step by Step

$$log(x + 3) + log(x) = 1$$ By rules of logarithmic functions: $log(x + 3) + log(x) = log(x)(x + 3) = log (x^{2} + 3x)$ Therefore, we can re-write the original equation as follows and solve accordingly: $log_{10}(x^{2} + 3x) = 1$ $10^{1} = (x^{2} + 3x)$ $0 = x^{2} + 3x - 10$; where 2 factors of 10 that,when substracted result in +3 are $5$ and $2$: $0=(x + 5)(x-2)$; where $x=-5$ or $x=2$. Since logarithms are not defined for negative values within the realm of Real numbers, the only solution is $x = 2$.
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