Precalculus (6th Edition) Blitzer

$1.5\ sec$, $44\ ft$
Step 1. Based on the given equatioin, we have $a=-16,b=48$ Step 2. The maximum will happen when $t=-\frac{b}{2a}=-\frac{48}{2(-16)}=1.5\ sec$ Step 3. We can get the maximum height as $s(1.5)=-16(1.5)^2+48(1.5)+8=44\ ft$