College Algebra (6th Edition)

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

Chapter 7 - Summary, Review, and Test - Cumulative Review Exercises (Chapters 1-7) - Page 7074: 6

Answer

$x = 1$

Work Step by Step

$$log_{3}(x) + log_{3}(x + 2) = 1$$ Since both logarithms have the same base, we can use the Rules of Logarithms to simplify the logarithmic terms as follows: $$log_{3}(x) + log_{3}(x + 2)$$ $$log_{3}(x)(x+2)$$ $$log_{3}(x^{2} + 2x)$$ And re-write the original equation: $$log_{3}(x^{2} + 2x) = 1$$ Finally, we can change the new logarithm into exponential form and solve accordingly: $$log_{3}(x^{2} + 2x) = 1$$ $$3^{1} = x^{2} + 2x$$ $3 = x^{2} + 2x$ $0 = x^{2} + 2x - 3$ which can be factorized since two factors of $3$ that, when substracted, yield $2$, are $3\times1$: $0 = (x + 3)(x - 1)$; where $x = -3$ and $x = 1$. Since $log_{3}(-3)$ is not a defined function, the only valid solution is $x = 1$.
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