SOLUTION: I am really having troubles with these word problems. the equation -16t^2 - 32t + 400 gives the height of a ball, thrown downward from the top of a 400 ft building with an ini

Question 762491: I am really having troubles with these word problems.

the equation -16t^2 - 32t + 400 gives the height of a ball, thrown downward from the top of a 400 ft building with an initial velocity of 32 ft/s. find the time it takes for the ball to reach a height of 96 ft
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!

First of all, I'll show you the plot of this equation:

You can see the height of the building at

So, the height of the ball is the same as the height of the building
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The problem doesn't ask you for it, but you can also see that
the ball hits the ground at about sec or so.
The height is zero, so
Solving:

Using quadratic formula:

My guess was pretty good
----------------------
They are asking you for when

Use quadratic formula

sec
This seems to agree with the plot
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Just for explanation, suppose the had been +

Here's the plot:

This is the case where the ball is thrown upward instead of down.
Hope all this helps

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