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 - Chapter Review - Page 536: 28

Answer

$x\approx2.30$ and $x\approx-1.76$.

Work Step by Step

$2x^{2}-x+8=16$ Subtracting $16$ from both sides, we obtain $2x^{2}-x+8-16=16-16$ $\implies 2x^{2}-x-8=0$ Comparing $2x^{2}-x-8=0$ with $ax^{2}+bx+c=0$, we see that $a=2, b=-1$ and $c=-8$. Using the quadratic formula, we have $x=\frac{-b\pm \sqrt {b^{2}-4ac}}{2a}=\frac{-(-1)\pm\sqrt {(-1)^{2}-4(2)(-8)}}{2(2)}$ $=\frac{1\pm\sqrt {65}}{4}$ So, the solutions are $x=\frac{1+\sqrt {65}}{4}\approx2.30$ and $x=\frac{1-\sqrt {65}}{4}\approx-1.76$.
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