The graph would be an upside down parabola with a vertex (3, 96) and the other point on the graph is (0, 42).

I used the vertex form which is y=a(x-h)^{2}+k of a quadratic equation to find a. By substitution 42 = a(0 - 3)^{2} + 96 so a = -6. Next, I let y=0 since 0 is the rocket hitting the ground. Next I solved the equation 0 = -6(x - 3)^{2} + 96 and x = 7. So it would take 7 seconds for the rocket to hit the ground.