SOLUTION: (This word problems involves using the quadratic formula) The height in feet of a ball thrown off the roof of a building is given by{{{h(t)=-16t^2+70t+75}}} , where t represents th

Question 304263: (This word problems involves using the quadratic formula) The height in feet of a ball thrown off the roof of a building is given by , where t represents the time in seconds since the ball was thrown. Determine to the nearest tenth of a second the time at which the ball strikes the ground at h=0. (steps will be appreciated)
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!

.
Set h(t) to zero and solve for t:

Solve by applying the quadratic formula. Doing so will yield:
t = {-0.9, 5.3}
We can toss out the negative solution leaving:
t = 5.3 seconds
.
Details of quadratic formula to follow:

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=9700 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: -0.890268063061283, 5.26526806306128. Here's your graph:

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