Pleeease me
a ball is thrown from the top of a 72ft building with a upward velocity of 24ft/s

a. when will it reach it maximum height

b. how far above the ground will it be

c. how long will it take for the ball to reach the gorund

show work if possible

A:  at 3/4, or 0.75 seconds

B:  81 feet

C:  3 seconds

Step-by-step explanation:

Since the function is a quadratic representing height, and the coefficient of the t² is negative, the vertex of the parabola will be the maximum height achieved by the ball.  

The general form for a quadratic equation is ax² + bx + c,

Our equation is h(t) = -16t² + 24t + 72

 here a is -16, and b is 24

To find the x coordinate of the vertex, use   x = -b/(2a)

We have x = -24/[2(-16)]

                 x = -24/-32

                          x = 3/4

So at 3/4 seconds, the ball reaches is maximum height

Now plug that into the equation to find the y value, which will be the height...

y = -16(3/4)² + 24(3/4) + 72  

      y = -16(9/16) + 72/4 + 72

           y = -9 + 18 + 72

               y =  81 feet

To see how long it took to reach ground, solve the equation..

0 = -16t² + 24t + 72

  0 = 2t² - 3t - 9      (divide both sides by -8)

      0  =  (2t + 3)(t - 3)

       so 2t + 3 = 0,  

                 t = -3/2    *this answer is ignored because t is time,so it must be positive

             and  t - 3 = 0

                        t = 3