(13 points) im super ( look at picture and show all work)) do the last ! (c)

The time to complete one jump is the difference in the values of t for which h(t) = 0. A graphing calculator shows this nicely, but you can also figure it out algebraically.

Since the quadratic has no constant term, it is easily factored.
  0 = -16t^2 + 28t
  0 = -4t(4t -7)
This product will be zero when one or both factors are zero.
For -4t = 0
  t = 0
For (4t -7) = 0
  4t = 7
  t = 7/4 = 1.75

This tells us the dolphin leaves the water at t=0 and completes the jump at t=1.75. The difference between these times is 1.75 - 0 = 1.75 seconds.

The length of time in seconds that it took the dolphin to complete one jump was
  1.75

Use a graph site then you will find your answer