Algebra II
posted by Jeannie on .
A rock is thrown upward with a velocity of 28 meters per second from the top of a 36 meter high cliff, and it misses the cliff on the way back down. When will the rock be 9 meters from the water below. Round to two decimal places.

we have
h(t) = 36 + 28t  4.9t^2
So, when h=9, just solve
36 + 28t  4.9t^2 = 9
t ~= 6.55 sec