Unit: Quadratics section: max/min word problems

i have no idea how to do this problem:

**A soccer ball lying on the ground is kicked downfield and hits the ground 62m away. If the max. height reached by the ball is 15m, algebraically determine the quadratic function that models this trajectory and use the function to calculate the height when it is 48m downfield.**
The answer is :

__ y= - 15/931(x-31)^2+15__ __height= 10.5m at 48 m downfield__
( ^2 means to the power of 2

)

My test is tomorrow so much help quickly would be greatlyy appreciated!!!