SOLUTION: I am completely lost! Please Help? If a stone is tossed from the top of a 350 meter building, the height of the stone as a function of time is given by h(t) = -9.8t2 � 10t + 350

Question 387764: I am completely lost! Please Help?
If a stone is tossed from the top of a 350 meter building, the height of the stone as a function of time is given by h(t) = -9.8t2 � 10t + 350, where t is in seconds, and height is in meters. After how many seconds will the stone hit the ground? Round to the nearest hundredth�s place; include units in your answer
Answer by jsmallt9(3758) (Show Source): You can put this solution on YOUR website!

Height is measured from the ground up. So when the stone hits the ground, its height will be zero. So the equation to solve is:

This is a quadratic equation. We already have a zero on one side so we proceed to the next step: Factor or use the Quadratic Formula. The expression on the right side will not factor so we must use the Quadratic Formula:

which simplifies as follows:

In long form this is:
or
The first equation gives us a negative value for t (because the numerator will be positive and the denominator is negative). Since time cannot be negative, we will reject the solution from that equation. So the only meaningful solution is:

This is an exact expression for the solution. If you want a decimal approximation then get out your calculator, find the square root and simplify the expression.
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