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The height of a ball when it is thrown off a cliff can be represented by the equation $h=45-7t-6t^2$, where $t$ is time in seconds. In how many seconds will the ball reach a height of 25 feet?

 Apr 27, 2019
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f(h)=45-7t-6t^2
Sub 25 for h and rearrange:
25 =45 - 7t - 6t^2
6t^2 + 7t - 45 + 25
6t^2 + 7t - 20 = 0
Solve for t using the Quadratic Formula
t = 4 /3 = 1 1/3 seconds.  t =- 5/2 (discard)

 Apr 27, 2019

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