College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 1 - Section 1.2 - Quadratic Equations - 1.2 Assess Your Understanding - Page 101: 30

Answer

$\{ -\displaystyle \frac{5}{2},1\}$

Work Step by Step

We exclude $x=-4$ and $x=2$ from the solutions, as the equation would not be defined. Multiply with the LCM, $(x+4)(x-2)$ $5(x-2)=4(x+4)(x-2) +3(x+4)$ Distribute and write in standard form. $5x-10=4(x^{2}+2x-8)+3x+12$ $5x-10=4x^{2}+8x-32+3x+12$ $5x-10=4x^{2}+11x-20$ $0=4x^{2}+6x-10$ ...divide with 2... $2x^{2}+3x-5=0$ We search for two factors of $(ac=-10)$, whose sum is $b=+3.$ ... we find $-2$ and $+5.$ Rewrite the LHS: $2x^{2}-2x+5x-5=0$ ... factor in pairs $2x(x-1)+5(x-1)=0$ $(2x+5)(x-1)=0$ Either $2x+5=0 \Rightarrow x=-\displaystyle \frac{5}{2}$ or $x=1$ (the restrictrions are not violated for either x) Solution set = $\{ -\displaystyle \frac{5}{2},1\}$
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