Question

A ball is thrown from the top row of seats in a stadium. The function h(t)=-16t^2+64t+80 gives the height, in feet, of the ball t seconds after it is thrown. How long will it be before the ball hits the ground?
I already found the maximum height, it's at 144 feet


A. 5

B. 16

C. 2

D. 9

Answer 1

Answer:

5 seccs

Step-by-step explanation:

Given the modeled function of the height expressed as;

h(t)=-16t^2+64t+80

The ball hits the ground when h(t) = 0 (when the height is zero)

Substitute into the function and find t;

0 =-16t^2+64t+80

divide through by -16

0 = t²-4t-5

Factorize;

t²-4t-5 = 0

t²-5t+t-5 = 0

t(t-5)+1(t-5) = 0

(t+1)(t-5) = 0

t + 1 = 0 and t-5 = 0

t = -1 and t = 5

Time can't be negative

Hence it will take the ball 5secs before it hits the ground