## Algebra and Trigonometry 10th Edition

$b=±20$
The $y$ of the vertex is $25$: $f(-\frac{b}{2a})=25$ $f(-\frac{b}{-2})=f(\frac{b}{2})=25$ $-(\frac{b}{2})^2+b(\frac{b}{2})-75=25$ $-\frac{b^2}{4}+\frac{b^2}{2}=100$ $\frac{b^2}{4}=100$ $b^2=400$ $b=±20$