Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 6 - Section 6.1 - Rational Expressions and Functions; Multiplying and Dividing - Exercise Set - Page 417: 136

Answer

It doesn't make sense

Work Step by Step

We have to simplify the given rational expression (if possible): $$\dfrac{2(x+2)-5(x+1)}{(x+2)(x+1)}.$$ Dividing the numerator and the denominator of a rational function by the denominator does not lead to a simplified fraction. It is the same thing as if we would rewrite the function as a sum of fractions and then simplify each of them separately: $$\begin{align*} \dfrac{2(x+2)-5(x+1)}{(x+2)(x+1)}&=\dfrac{2(x+2)}{(x+2)(x+1)}-\dfrac{5(x+1)}{(x+2)(x+1)}\\ &=\dfrac{2}{x+1}-\dfrac{5}{x+2}. \end{align*}$$ So it makes little sense to divide the numerator by the denominator (and obtain the above decomposition) and to divide the denominator by the denominator and obtain $1$. The most common approach to obtain a simplified fraction is to first factor both numerator and denominator and afterwards look for common factors and simplify them. $$\dfrac{2(x+2)-5(x+1)}{(x+2)(x+1)}=\dfrac{2x+4-5x-5}{(x+2)(x+1)}=\dfrac{-3x-1}{(x+2)(x+1)}.$$ We cannot simplify further.
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