SOLUTION: a toy rocket is launched from a 2.1 m high platform in such a way that its height, h (in meters), after t seconds is given by the equation h= -4.9t^2 + 14.0t + 2.1. How long will i

Question 344463: a toy rocket is launched from a 2.1 m high platform in such a way that its height, h (in meters), after t seconds is given by the equation h= -4.9t^2 + 14.0t + 2.1. How long will it take for the rocket to hit the ground?
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
Set h to zero and solve for t:
h= -4.9t^2 + 14.0t + 2.1
0= -4.9t^2 + 14.0t + 2.1
Apply quadratic formula to get:
t = {-0.143, 3}
You can toss out the negative solution leaving:
t = 3 seconds
.
Details of quadratic to follow:

Solved by pluggable solver: SOLVE quadratic equation with variable

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=237.16 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: -0.142857142857143, 3. Here's your graph:

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