Intermediate Algebra: Connecting Concepts through Application

Published by Brooks Cole
ISBN 10: 0-53449-636-9
ISBN 13: 978-0-53449-636-4

Chapter 4 - Quadratic Functions - 4.5 Solving Equations by Factoring - 4.5 Exercises - Page 361: 71

Answer

$y=x^2+4x-21$

Work Step by Step

Recall: If $a$ and $b$ are zeros of a quadratic function and there is no constant multiplier, then the equation of the function is $y=(x-a)(x-b)$. The quadratic function has the zeros $3$ and $-7$ and there is no constant multiplier. Thus, the equation of the quadratic function must be: \begin{align*} y&=(x-3)[x-(-7)]\\ y&=(x-3)(x+7)\\ y&=x^2+7x-3x-21\\ y&=x^2+4x-21 \end{align*}
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