Answer
$b=±20$
Work Step by Step
The $y$ of the vertex is $25$:
$f(-\frac{b}{2a})=25$
$f(-\frac{b}{-2})=f(\frac{b}{2})=25$
$-(\frac{b}{2})^2+b(\frac{b}{2})-75=25$
$-\frac{b^2}{4}+\frac{b^2}{2}=100$
$\frac{b^2}{4}=100$
$b^2=400$
$b=±20$
Algebra and Trigonometry 10th Edition
by Larson, Ron
Published by
Cengage Learning
ISBN 10:
9781337271172
ISBN 13:
978-1-33727-117-2
Chapter 3 - 3.1 - Quadratic Functions and Models - 3.1 Exercises - Page 250: 77
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