Answer
$V_0=80$ ft/s
Work Step by Step
$16t^2-V_0t+h=0$, $h=100$.
$16t^2-V_0t+100=0$
Using $b^2-4ac=0$ determinant...
$V_0^2-4(16)(100)=0$,
$V_0^2-6400=0$,
$V_0^2=6400$,
$V_0=\pm 80$,
Since we are solving for speed here, only the positive answers are relevant. Therefore, $V_0=80$ ft/s
