Question

A volleyball reaches its maximum height of 13 feet, 3 seconds after its served. Which of the following quadratics could model the height of the vollyball over time after it is served. Select all that apply.

A: f(x)=2x^2+12x+5
B: f(x)=-2x^2+12x-5
C: f(x)=-2x^2-12x+5
D: f(x)=-2(x-3)^2+13
E: f(x)=-2(x+3)^2+13

Answer 1

notice the picture below

that's when it reaches the highest point, at the "vertex"
what's the vertex at? is at h,k

where
`\bf f(x)=a(x-h)^2+k\qquad \begin{array}{lllll} vertex&(&h&,&k)\\ &&\uparrow &&\uparrow \\ &&3&&13 \end{array}`