a golf ball is hit straight upwards at v=64 ft/sec. Use the model y=-16x^2+vx for the height of the ball y, in feet, at the time x in seconds.
a. find the vertex. min or max
b. what is the maximum height of the golf ball
c. how long does it take to reach this height
d. how long is the ball in the air

i know that you need to use the vertex formula somewhere in there.
y=a(x-h)^2=k

but i don’t know where to go from there..

Question

a golf ball is hit straight upwards at v=64 ft/sec. Use the model y=-16x^2+vx for the height of the ball y, in feet, at the time x in seconds.
a. find the vertex. min or max
b. what is the maximum height of the golf ball
c. how long does it take to reach this height 
d. how long is the ball in the air

i know that you need to use the vertex formula somewhere in there. 
y=a(x-h)^2=k

but i don’t know where to go from there..