algebra
posted by Haiti .
You throw a tennis ball up in the air from an initial height of 4 feet and an initial velocity of 36 feet per
second. Will the ball reach a height of 30 feet? If so, how long will it take?

you should know that
height = 16t^2 + 36t + 4
so 30 = 16t^2 + 36t + 4
16t^2  36t + 26 = 0
8t^2  18t + 13 = 0
use the quadratic equation to solve for t
( you should get an imaginary root, so the ball never reaches a height of 30 feet)