h=-16t^2+8t+360

Question

A ball is thrown straight up from a rooftop 360ft high. The formula h=−16t2+8t+360 describes the​ ball's height above the​ ground, h, in​ ft, t seconds after it was thrown. The ball misses the rooftop on its way down and strikes the ground. How long will it take for the ball to hit the​ ground?

The ball hits the ground after _ seconds.

Each tick mark represents _ ​second(s).

Answer 1

-16t^2 + 8t +360 = 0 multiply by -1

16t^2 - 8t -360 =0 divide by 8

2t^2 - t - 45 = 0 factor

(2t+9)(t-5) = 0, set the factor = 0 and solve for t, ignore the negative t value

t=5

the ball hits the ground in 5 seconds