Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 7 - Review - Concept Check - Page 537: 3

Answer

The statement is False. $$ \frac{x^{2}+4}{x^{2}\left(x-4\right) } $$ It can be put in the form: $$ \frac{A}{x^{2}}+\frac{B}{x}+\frac{C}{x-4} $$ In fact, $A = −1, B = \frac{-1}{4} $ and $C =\frac{5}{4} $.

Work Step by Step

Resolve into partial fractions $$ \frac{x^{2}+4}{x^{2}\left(x-4\right) } $$ We’ll first factor the denominator and then get the form of the partial fraction decomposition as follows: $$ \begin{aligned} \frac{x^{2}+4}{x^{2}\left(x-4\right) } & =\frac{A}{x^{2}}+\frac{B}{x}+\frac{C}{x-4}\\ &=\frac{A\left(x-4\right)+Bx\left(x-4\right)+Cx^{2} } {x^{2 }\left(x-4\right) } \end{aligned} $$ multiplying both sides by the denominator, we get: $$ x^2+4=A\left(x-4\right)+Bx\left(x-4\right)+Cx^{2} $$ Substituting $x = 0 $ into this equation gives $A = −1$, substituting $x = 4$ gives $ C= \frac{5}{4}$, and substituting $x =1 $ gives $ B = \frac{-1}{4}$ so that $$ \frac{x^{2}+4}{x^{2}\left(x-4\right) }=\frac{-1}{x^{2}}+\frac{\frac{5}{4}}{x}-\frac{\frac{1}{4}}{x-4} $$ Thus, the statement is False. It can be put in the form: $$ \frac{A}{x^{2}}+\frac{B}{x}+\frac{C}{x-4} $$ In fact, $A = −1, B = \frac{-1}{4}, C = \frac{5}{4}$
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