Solving Quadratic Equations

Quote:

Example 3: When a football is kicked with a vertical speed of 20m/s, its height,

*h* metres, after

*t* seconds is given by the formula:

How long after the kick is the football at a height of 15m?

Solution

Substitute 15 for

*h* in the formula:

This produces a quadratic equation. The solution of the equation gives the times when the height is 15m.

Collect all the terms on one side of the equation.

Either

or

The football is at a height of 15m twice: first on the way up, 1 s after the kick, then on the way down, 3 s after the kick.

So I got this question:

A baseball is hit with a vertical speed of 31.3m/s. Use the formula in the modelling box following Example 3. How long after being hit is the ball at a height of 25m? Give your answer to 1 decimal place.

How exactly do I form the equation? I got it but I don't think I'm on the right track. Thanks a bunch.