SOLUTION: A ball is thrown vertically upwars of 15 feet per second from a bridge that is 55 feet above the level of the water. The height h, in feet, of the ball above the water at time t in

Question 479539: A ball is thrown vertically upwars of 15 feet per second from a bridge that is 55 feet above the level of the water. The height h, in feet, of the ball above the water at time t in seconds after it is thrown is h = 12t^2 + 20t - 48
Find the time when the ball strikes the water.
Answer by jorel1380(3719) (Show Source): You can put this solution on YOUR website!
55=12t^2 + 20t - 48
12t^2 + 20t -103=0

Solved by pluggable solver: SOLVE quadratic equation with variable

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=5344 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 2.21261114708284, -3.87927781374951. Here's your graph:

t=2.21261114708284, -3.8792778137495
Throwing out the negative answer, we get t=2.21261114708284 seconds..
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