SOLUTION: A rock is thrown from the top of a tall building. The distance, in feet, between the rock and the ground t seconds after it is thrown is given by d=-16t^2-2t+733. How long after th

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Question 982622: A rock is thrown from the top of a tall building. The distance, in feet, between the rock and the ground t seconds after it is thrown is given by d=-16t^2-2t+733. How long after the rock is thrown is it 400 feet from the ground?
Answer by macston(5194)   (Show Source): You can put this solution on YOUR website!
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400=-16t^2-2t+733
0=-16t^2-2t+333
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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=21316 is greater than zero. That means that there are two solutions: .




Quadratic expression can be factored:

Again, the answer is: -4.625, 4.5. Here's your graph:

The answer that makes sense here is 4.5 seconds
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