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: 112

Answer

$x=4$ and $x=9$

Work Step by Step

$x-5\sqrt{x}+6=0$ Let $\sqrt{x}$ be equal to $u$: $u=\sqrt{x}$ $u^{2}=x$ Rewrite the original equation using the new variable $u$: $u^{2}-5u+6=0$ Solve this equation by factoring: $(u-3)(u-2)=0$ Set both factors equal to $0$ and solve each individual equation for $u$: $u-3=0$ $u=3$ $u-2=0$ $u=2$ Substitute $u$ back to $\sqrt{x}$ and solve for $x$: $u=3$ $\sqrt{x}=3$ $x=9$ $u=2$ $\sqrt{x}=2$ $x=4$ The two solutions found are $4$ and $9$ and the original equation is true for both of them. The final answer is: $x=4$ and $x=9$
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