Hello, kkmarie9009!

The function is a quadratic (second degree).

. . Its graph is a down-opening parabola.

. . The maximum height occurs at the vertex of the parabola.

The formula for the vertex of a parabola is:

Our parabola has:

The vertex is at:

(a) Therefore, the rock reaches maximum height at

seconds.

If

, then:

(b) Therefore, the maximum height is:

m.

If the rock hits the ground, its height is zero.

. . Solve the quadratic:

Quadratic Formula:

Hence:

(c) Therefore, the rock hits the ground in about

seconds.