Big Ideas Math - Algebra 1, A Common Core Curriculum

Published by Big Ideas Learning LLC
ISBN 10: 978-1-60840-838-2
ISBN 13: 978-1-60840-838-2

Chapter 9 - Solving Quadratic Equations - 9.4 - Solving Quadratic Equations by Completing the Square - Exercises - Page 511: 31

Answer

$x=8$ and $x=-1$

Work Step by Step

$2x^{2}-14x+10=26$ Subtracting $10$ from both sides we get $2x^{2}-14x=16$ Divide both sides of the equation by $2$ to obtain $x^{2}-7x=8$ Add $(\frac{b}{2})^{2}=(\frac{-7}{2})^{2}=(\frac{7}{2})^{2}$ to both sides to complete the square. $x^{2}-7x+(\frac{7}{2})^{2}=8+(\frac{7}{2})^{2}$ $\implies (x-\frac{7}{2})^{2}=8+\frac{49}{4}$ $\implies (x-\frac{7}{2})^{2}=\frac{81}{4}$ Taking square root on both sides, we have $x-\frac{7}{2}=\pm\frac{9}{2}$ $\implies x=\frac{7}{2}\pm \frac{9}{2}$ The solutions of the given equation are $x=\frac{7}{2}+\frac{9}{2}=8$ and $x=\frac{7}{2}-\frac{9}{2}=-1$
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