calculus
posted by fred .
If a ball is thrown vertically upward with a velocity of 160 ft/s, then its height after t seconds is s = 160t  16t^2
What is the velocity of the ball when it is 96 ft above the ground on its way up?

Solve the equation
16t^2 160t +96 = 0
There will be two roots. Take the lowest t value as the solution. That will be the answer when the ball is going up.
Note that the equation can be simplifed to
t^2 10t + 16 = 0
which factors easily.