The height of a ball above the ground t seconds it is thrown is h () = - 16^2 + 32 + 20. How long will it take for the ball to hit the ground?

Answer: 5/2 or 2.5 seconds

Step-by-step explanation:

When the ball hits the ground, the height is 0. We can set the equation equal to 0 to find how long it takes to hit the ground.

You didn't include time in your equation, I will assume the equation is h (t) = -16t²+32t+20. If not, let me know and I will fix it.

-16t²+32t+20=0

-4 (4t²-8t-5) = 0

4t²-8t-5=0

t=5/2 and t=-1/2 [quadratic formula]

We know our time cannot be t=-1/2 because you can't have negative time. Therefore, our time is t=5/2 or 2.5 seconds.