A ball is thrown, and the height (in meters) as a function of time (in seconds) is h = -5t2 + 20t + 2.

How long was the ball in the air?

(4 seconds)

Step-by-step explanation:

Basically:

All you have to do is find the distance between the 2 roots of the parabola

By plugging in the value of a=-5, b=20, and c=2 into the quadratic formula:  

      Quadratic Formula = x=( -b±√(b^2-4*a*c))/(2*a)

We get 2 roots :

a) (10-√110)/5

b) (10+√110)/5

And then we add the 2 roots, thus getting 4

ANSWER: 4 seconds