Question

7. The height of a ball in meters is modeled

by f(x) = -5x2 + 40x, where x is the time
in seconds after it is hit. How long is the
ball in the air?

Answer 1

the ball is in the air for 8 seconds

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