Question

A ball is thrown from an initial height of 1 meter with an initial upward velocity of 9 m/s. The ball's height h (in meters) after t seconds is given by the following
h=1+9t-5t^2
Find all the values of the t for which the ball's height is 4 meters.

Answer 1

two values ... going up and coming down

4 = 1 + 9 t - 5 t^2 ... 5 t^2 - 9 t + 3 = 0

use quadratic formula to find t

Answer 2

ergf