College Algebra (11th Edition)

Published by Pearson
ISBN 10: 0321671791
ISBN 13: 978-0-32167-179-0

Chapter 1 - Section 1.6 - Other Types of Equations and Applications - Summary Exercises on Solving Equations - Page 136: 18

Answer

$x=4$

Work Step by Step

We are given: $\sqrt{x}+1=\sqrt{11-\sqrt{x}}$ We square both sides: $(\sqrt{x}+1)^{2}=(\sqrt{11-\sqrt{x}})^{2}$ $(\sqrt{x}+1)(\sqrt{x}+1)=(\sqrt{11-\sqrt{x}})(\sqrt{11-\sqrt{x}})$ $x+2\sqrt{x}+1=11-\sqrt{x}$ $x+2\sqrt{x}+1+\sqrt{x}=11$ $x+3\sqrt{x}+1=11$ $3\sqrt{x}=10-x$ We square both sides again: $(3\sqrt{x})^{2}=(10-x)^{2}$ $9x=100-20x+x^{2}$ $100-29x+x^{2}=0$ $x^{2}-29x+100=0$ And factor: $(x-4)(x-25)=0$ Equate each factor to zero, then solve each equation for $x$: $(x-4)=0$ or $(x-25)=0$ $x=4$ or $x=25$ However, the solution $x=25$ does not work in the original equation: $\sqrt{25}+1=\sqrt{11-\sqrt{25}}$ $5+1=\sqrt{11-5}$ $6=\sqrt{6}$ $36=6$ Since we got a false statement, the solution $x=25$ does not work. Hence the only solution is $x=4$.
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