If a baseball player hits a baseball from 4 feet off the ground with an initial velocity of 64 feet per second, how long will it take the baseball to hit the ground? Use the equation h = –16t2 + 64t + 4.

Question

ash2326 · Answer

h=-16t^2+64t+4
t=0 the ball is at height 4 feet
this can also be verified from the given equation
we have to find value of t for which h=0
0=-16t^2+64t+4
or
4t-16t-1=0
we know that 
ax^2+bx+c=0
$$x=(-b \pm \sqrt(b^2-4ac))/2a$$

here a=4 b=-16
c=-1

so 
$$t=(16 \pm \sqrt(16^2-4*4*(-1))/8$$
$$t=(16 \pm \sqrt(272))/8$$
or $$t=(16 \pm 16 \sqrt 17)/8$$
t= 2 + 2 root 17
or t= 2- 2 root 17
t= 2-2 root 17 <0
so our solution is
t= 2+ 2 root 17
$$t=2(1+ \sqrt 17)$$
t=10.2462 seconds

anonymous · Answer

t=(16±(√272))/8
t=(16±(√16*√17))/8
t=(16±(4√17))/8
and that's where I'm stuck