Question

A ball is thrown in the air from a ledge. Its height in feet is represented by 

Answer 1

check the picture below.

$\bf \stackrel{f(x)}{0}=-16(x^2-6x-7)\implies 0=x^2-6x-7 \\\\\\ 0=(x-7)(x+1)\implies x= \begin{cases} \boxed{7}\\ -1 \end{cases}$

it cannot be -1, because is a seconds amount after moving.