Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 1 - Section 1.5 - Equations - 1.5 Exercises - Page 57: 109

Answer

The solutions to this equation are $x=-1,$ $x=0$ and $x=3$

Work Step by Step

$4(x+1)^{1/2}-5(x+1)^{3/2}+(x+1)^{5/2}=0$ Take out common factor $(x+1)^{1/2}$: $(x+1)^{1/2}[4-5(x+1)+(x+1)^{2}]=0$ Rearrange the expression inside brackets: $(x+1)^{1/2}[(x+1)^{2}-5(x+1)+4]=0$ Let $x+1$ be equal to $u$: $u^{1/2}(u^{2}-5u+4)=0$ Set both factors equal to $0$ and solve each individual equation for $u$: $u^{1/2}=0$ $u=0$ $u^{2}-5u+4=0$ (Solve this second equation by factoring): $(u-1)(u-4)=0$ Again, set both factors equal to $0$ and solve each individual equation for $u$: $u-1=0$ $u=1$ $u-4=0$ $u=4$ Substitute $u$ back to $x+1$ into each solution and solve for $x$: $u=0$ $x+1=0$ $x=-1$ $u=1$ $x+1=1$ $x=1-1$ $x=0$ $u=4$ $x+1=4$ $x=4-1$ $x=3$ The original equation is true for all values of $x$ found. The solutions to this equation are $x=-1,$ $x=0$ and $x=3$
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