SOLUTION: I came across this question, and I got completely stuck. Please help? "A ball is thrown downward with an initial velocity of 21 meters per second from a cliff that is 90 meters h

Question 748269: I came across this question, and I got completely stuck. Please help?
"A ball is thrown downward with an initial velocity of 21 meters per second from a cliff that is 90 meters high. The height of the ball is given by the quadratic equation h=-4.9t^2-21t+110 where h is in meters and t is the time in seconds since the ball was thrown. Find the time that the ball will be 60 meters from the ground. Round your answer to the nearest tenth of a second."
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
h=-4.9t^2-21t+110
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h(t) = -4.9t^2 - 21t + 90 It starts at 90 m high, h(0) = 90, not 110
h(t) = -4.9t^2-21t + 90 = 60 solve for t
-4.9t^2 - 21t + 30 = 0

Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=1029 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: -5.41612549639703, 1.13041121068274. Here's your graph:

===================
Ignore the negative solution
t = 1.13 seconds
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