Answer:
the ball is in the air for 8 seconds
Step-by-step explanation:
f(x) = y
when y = 0, the ball would've travelled through the air over the final time of flight.
0 = -5x^2 + 40x + 0
use quadratic equation to find the value of x
x = (-b ± √b^2 - 4 • a • c) / 2 • a
x = (-40 ± √40^2 - 4 • -5 • 0) / 2 • -5
x = (-40 ± √1600) / - 10
x = (-40 ± 40) / - 10
x = 0 or x = 8
