Answer
a) 720 ft
b) 384 ft
c) 7 seconds
d) $16*(7-t)(7+t)$
Work Step by Step
a)
$t=2$
$h=784-16t^2$
$h=784-16*2^2$
$h=784-16*4$
$h=784-64$
$h=720$
b)
$t=5$
$h=784-16t^2$
$h=784-16*5^2$
$h=784-16*25$
$h=784-400$
$h=384$
c)
$h=784-16t^2$
$0=784-16t^2$
$16t^2=784$
$16t^2/16=784/16$
$t^2 = 49$
$\sqrt {t^2} = \sqrt {49}$
$t=±7$
We can't have a negative time, so $t=7$.
d)
$784-16t^2$
$16(49-t^2)$
$16*(7-t)(7+t)$