How do I state the height of the equation h= -4.9t^2 +Vo +Ho in vertex form and how do I determine the initial velocity?

Question

Mrs. Varga is placed in a human cannon her flight path is modelled by h= -4.9t^2 +Vo +Ho, where Vo is the initial velocity and Ho is the initial height. She reached a maximum height of 70m after 2 seconds and landed in a pond.

Answer 1

h = -4.9t^2 + vot = ho

h' = -9.8t + vo = 0

t = vo/9.8 = 2

vo = 9.8x2 = 19.6 m/sec = initial velocity

70=-4.9(2^2) +19.6(2) +ho = 39.2-19.6 = 19.6 +ho

ho = 70-19.6 = 50.4 meters = initial height