How to derive the formula for the final velocities of 2 objects?

Question

I dont know how to

Derive the formula for the final velocities of the 2 objects which underwent an elastic collision as a function of known quantities m1, m2, v01, v02

Also what happens to the final velocities if m1=m2

Answer 1

use kinetic energy, 1/2mv^2. Since elastic, the total energy before the collision is the same as after.

Also, can use momentum before and after, P = mv, which is always conserved, even in inelastic collisions.