a person standing close to the edge on the top of a 96 foot building throws a ball vertically upwards. the quadratic function h(t)= -16t^2 + 80t + 96 models the balls height about the ground, h(t) in feet, t seconds after it was thrown. what's the maximum height of the ball?

Respuesta :

Let's compute h'(t) to find its maximum:

[tex]h^{\prime}(t)=-32t+80[/tex]

In order to find its maximum, we equal it to 0, solve for t and replace the value we get in h(t):

[tex]-32t+80=0[/tex]

From this

[tex]t=\frac{5}{2}[/tex]

Substituting in h(t) we get:

[tex]-16(\frac{5}{2}^{})^2+80(\frac{5}{2})+96=196[/tex]

Thus the maximum height of the ball will be 196 feet.

In order to know how many seconds will pass until the ball hits the ground, we must solve h(t)=0

[tex]-16t^2+80t+96=0[/tex]

From this we get:

[tex]t_1=-1,t_2=6[/tex]

Since it doesn't make sense for the ball to hit the ground in negatve time, the ball will hit the ground after 6 seconds.