jmc

Question

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?

Accepted Answer

If we plug in 25 for h, we get align* 25& =45-7t-6t^2 6t^2+7t-20& =0 (3t-4)(2t+5)& =0 align*The two possible values of t are 43, and -52. Since the time can only be a positive value, the answer must be 43.