Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 11 - Quadratic Functions and Equations - 11.2 The Quadratic Formula - 11.2 Exercise Set - Page 713: 32

Answer

$x=15$ or $x=1$

Work Step by Step

$ 11(x-2)+(x-5)=(x+2)(x-6)\qquad$... use the distributive property: $a(b+c)=ab+ac$. $ 11x-22+x-5=(x+2)(x-6)\qquad$... use the FOIL method. $ 11x-22+x-5=x^{2}-6x+2x-12\qquad$...add like terms. $ 12x-27=x^{2}-4x-12\qquad$...add $(-x^{2}+4x+12)$ to both sides. $ 12x-27-x^{2}+4x+12=x^{2}-4x-12-x^{2}+4x+12\qquad$...add like terms. $-x^{2}+16x-15=0\qquad$...mulitiply both sides by $-1$. $ x^{2}-16x+15=0\qquad$... solve with the Quadractic formula. $a=1,\ b=-16,\ c=15$ $ x=\displaystyle \frac{-b\pm\sqrt{b^{2}-4ac}}{2a}\qquad$... substitute $b$ for $-16,\ a$ for $1$ and $c$ for $15$. $ x=\displaystyle \frac{-(-16)\pm\sqrt{(-16)^{2}-4\cdot(15)\cdot 1}}{2\cdot 1}\qquad$... simplify. $x=\displaystyle \frac{16\pm\sqrt{256-60}}{2}$ $x=\displaystyle \frac{16\pm\sqrt{196}}{2}$ $ x=\displaystyle \frac{16\pm 14}{2}\qquad$... the symbol $\pm$ indicates two solutions. $x=\displaystyle \frac{16+14}{2}=\frac{30}{2}=15$ or $x=\displaystyle \frac{16-14}{2}=\frac{2}{2}=1$
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