Question

When will the ball be 10 ft in the air?

Answer 1

We have the next quadratic function

`f(x)=-16x^2+64x+5`

The question give us f(x)=10ft

`\begin{gathered} 10=-16x^2+64x+5 \\ -16x^2+64x+5-10=0 \\ -16x^2+64x-5=0 \end{gathered}`

so we will use the formula to solve quadratic functions

`x_(1,2)=\frac{-b\pm\sqrt[]{b^2-4ac}}{2a}`

where

a=-16

b=64

c=-5

we substitute the values

`x_(1,2)=\frac{-64\pm\sqrt[]{64^2-4(-16)(-5)}}{2(-16)}`

`x_(1,2)=\frac{-64\pm\sqrt[]{4096-320}}{-32}_{}`