SOLUTION: A ball is thrown from a height of 141 feet with an initial downward velocity of 21 ft/s. The balls height “h” (in feet) after “t” seconds is given by the following. H=141

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Question 1145786: A ball is thrown from a height of 141 feet with an initial downward velocity of 21 ft/s. The balls height “h” (in feet) after “t” seconds is given by the following.
H=141-21t-16t squared
How long after the ball is thrown does it hit the ground?
Round to the nearest hundredth
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
H=141-21t-16t squared
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Impact is at h = 0
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h = 141 - 21t - 16t^2 = 0
-16t^2 - 21t + 141 = 0
Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
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=9465 is greater than zero. That means that there are two solutions: .




Quadratic expression can be factored:

Again, the answer is: -3.69650723623841, 2.38400723623841. Here's your graph:


Ignore the negative solution.
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