Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Appendix A - Review - A.6 Solving Equations - A.6 Assess Your Understanding - Page A52: 92

Answer

$\left\{\dfrac{3-\sqrt {17}}{4},\dfrac{3+\sqrt {17}}{4}\right\}$

Work Step by Step

Add $1$ to both sides. $2x^2-3x-1+1=0+1$ Simplify. $2x^2-3x=1$ Divide both sides by $2$. $x^2-\dfrac{3}{2}x=\dfrac{1}{2}$ Complete the square by adding $\left(\dfrac{-\frac{3}{2}}{2}\right)^2=\dfrac{9}{16}$ to both sides. $x^2-\dfrac{3}{2}x+\dfrac{9}{16}=\dfrac{1}{2}+\dfrac{9}{16}$ Simplify. $x^2-\dfrac{3}{2}x+\dfrac{9}{16}=\dfrac{8+9}{16}$ $x^2-\dfrac{3}{2}x+\dfrac{9}{16}=\dfrac{17}{16}$ Factor the left side. $\left(x-\dfrac{3}{4}\right)^2=\dfrac{17}{16}$ Take the square root of both sides. $x-\dfrac{3}{4}=\pm \sqrt {\dfrac{17}{16}}$ $x-\dfrac{3}{4}=\pm\dfrac{\sqrt {17}}{4}$ Split the expression to obtain: $x-\dfrac{3}{4}=\dfrac{\sqrt {17}}{4}\quad $ or $\quad x-\dfrac{3}{4}=-\dfrac{\sqrt {17}}{4}$ Add $\frac{3}{4}$ to both sides of both equations. $x-\dfrac{3}{4}+\dfrac{3}{4}=\dfrac{\sqrt {17}}{4}+\dfrac{3}{4}\quad$ or $\quad x-\dfrac{3}{4}+\dfrac{3}{4}=-\dfrac{\sqrt {17}}{4}+\dfrac{3}{4}$ Simplify. $x=\dfrac{3+\sqrt {17}}{4}\quad$ or $\quad x=\dfrac{3-\sqrt {17}}{4}$ Hence, the solution set is $\left\{\dfrac{3-\sqrt {17}}{4},\dfrac{3+\sqrt {17}}{4}\right\}$.
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