What is this answer? Please show steps because I am confused.

Question

suppose a bullet is fired into the air from a platform 8ft above the ground with an initial velocity of 2800ft/s. (hint: use h(t) = -16t^2+vot+ho)

what is the maximum height?

when does the bullet hit the ground?

find the average velocity from t=65 to t=70

find the average velocity from t=120 to t=125

Answer 1

As the platform is 8 ft above the ground h0 = 8

and v0 = 2800

So h(t) = -16t^2 + 2800t + 8

To find maximum height plot on Desmos (y = -16x^2 + 2800x + 8) and read off the largest y value

Find the x intercept - this will be the time when it hits the ground (s)

Average velocity from t=65 to t=70 = (distance travelled / time ) = [ h(70) - h(65) ] / 5

For the last : [ h(120) - h (125) ] / 5, { have switched the 120 and 125 around because it is falling then ]