H (x) = - 5x2 + 10x + 15

What is the height of the stone at the time it is thrown?

The height of the stone at the time it is thrown is 15.

Step-by-step explanation:

You have a quadratic function of the form h (x) = ax² + bx + c. In this case it is h (x) = - 5x²+10x+15, where a = -5, b = 10, c = 15, x is the time and h (x) is the height of the stone after being thrown.

The moment the stone is thrown is instant zero. So if x = 0, h (0) is calculated:

h (0) = - 5*0² + 10*0 + 15

h (0) = 0 + 0 + 15

h (0) = 15

The height of the stone at the time it is thrown is 15.