math
posted by bill .
A projectile is fired directly upward with a muzzle velocity of 860 feet per second from a height of 7 feet above the ground.
a. Determine a function for the height of the projectile t seconds after itâ€™s released.
b. How long does it take the projectile to reach of height of 100 feet on its way up?
c. How long is the projectile in the air?

height(t) = 16t^2 + 860t + 7
b) solve 100 = 16t^2 + 860t + 7 and use the smaller of the two t values you find
c) set height(t) = 0 and solve