Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 8 - Summary Exercises - Applying Methods for Solving Quadratic Equations - Page 531: 24

Answer

$x=\dfrac{2}{3}$

Work Step by Step

Squaring both sides, the given equation, $ x\sqrt{3}=\sqrt{2-x} ,$ is equivalent to \begin{align*} \left(x\sqrt{3}\right)^2&=\left(\sqrt{2-x}\right)^2 \\ x^2(3)&=2-x \\ 3x^2&=2-x \\ 3x^2+x-2&=0 .\end{align*} Using factoring of trinomials, the equation above is equivalent to \begin{align*} (x+1)(3x-2)&=0 .\end{align*} Equating each factor to zero (Zero Product Property), then \begin{array}{l|r} x+1=0 & 3x-2=0 \\ x=-1 & 3x=2 \\\\ & x=\dfrac{2}{3} .\end{array} Checking by substituting the solutions in the given equation results to \begin{array}{l|r} \text{If }x=-1: & \text{If }x=\dfrac{2}{3}: \\\\ -1\sqrt{3}\overset{?}=\sqrt{2-(-1)} & \dfrac{2}{3}\sqrt{3}\overset{?}=\sqrt{2-\dfrac{2}{3}} \\\\ -\sqrt{3}\overset{?}=\sqrt{2+1} & \dfrac{2\sqrt{3}}{3}\overset{?}=\sqrt{\dfrac{6}{2}-\dfrac{2}{3}} \\\\ -\sqrt{3}\ne\sqrt{3} & \dfrac{2\sqrt{3}}{3}\overset{?}=\sqrt{\dfrac{4}{3}} \\\\ & \dfrac{2\sqrt{3}}{3}\overset{?}=\sqrt{\dfrac{4}{3}\cdot\dfrac{3}{3}} \\\\ & \dfrac{2\sqrt{3}}{3}\overset{?}=\sqrt{\dfrac{4}{9}\cdot3} \\\\ & \dfrac{2\sqrt{3}}{3}\overset{?}=\sqrt{\dfrac{4}{9}}\cdot\sqrt{3} \\\\ & \dfrac{2\sqrt{3}}{3}\overset{?}=\dfrac{2}{3}\cdot\sqrt{3} \\\\ & \dfrac{2\sqrt{3}}{3}\overset{\checkmark}=\dfrac{2\sqrt{3}}{3} .\end{array} Since $x=-1$ does not satisfy the original equation then the only solution of the equation $ x\sqrt{3}=\sqrt{2-x} $ is $x=\dfrac{2}{3}$.
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