When can you use the Range Equation when trying to solve a Kinematics problem?

Question

What do you look for to know you can use it?

Answer 1

The range equation that is listed in most Physics texts assumes that the projectile is fired at an angle and follows a parabolic trajectory and comes back to the same height at which it is fired. You cannot use it for something fired from a height (eg a cannon fired from a cliff top) or even a horizontal projectile as they always need a height difference.