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 7 - Polynomial Equations and Factoring - 7.5 - Factoring x 2 + bx + c - Exercises - Page 389: 38

Answer

The solutions are $b=5$ and $b=3$.

Work Step by Step

$b^{2}+5=8b-10\implies b^{2}-8b+15=0$ To factor the polynomial $b^{2}+db+c$ to $(b+p)$ and $(b+q)$, we need to have $p+q=d$ and $pq=c$. In this case, $d=-8$ and $c=15$. $\implies p=-5$ and $q=-3$. Then, $b^{2}-8b+15=(b-5)(b-3)$ $b^{2}-8b+15=0\implies (b-5)(b-3)=0$ Using zero-product property, we have $b-5=0$ or $b-3=0$ $\implies b=5$ or $b=3$ The solutions are $b=5$ and $b=3$.
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