College Algebra (6th Edition)

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

Chapter P - Prerequisites: Fundamental Concepts of Algebra - Exercise Set P.6 - Page 86: 18

Answer

$2$; $x\ne-2, 2$

Work Step by Step

Before we multiply two fractions, we should factor each to see if we can cancel any terms. Top-left: $x^{2}-4$ is a difference of squares and factors to $(x + 2)(x - 2)$. Bottom-left: We have a perfect square trinomial, which factors to $(x - 2)(x - 2)$. Top-right: We can pull out a greatest common factor of $2$, leaving us with $2(x - 2)$. $\frac{(x+2)(x-2)}{(x-2)(x-2)}\times \frac{2(x-2)}{x+2}$ Note that virtually everything cancels: the $x-2$ terms on the left fraction, as well as a cross-canceled $x + 2$ and $x - 2$. The only part left is the $2$ in the numerator of our right-hand fraction. Thus, our answer is $2$. Also note that this is true only if $x\ne-2, 2$, since they make the original denominators equal to 0.
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