Inelastic Collision Energy loss

[camorin]

Homework Statement

Two particles are in a perfectly inelastic collision with no external force acting on them. Particle 1 has m1 and v1>0. Particle 2 has mass m2 and v2<0. Find the loss in kinetic energy after the collision. Express your answer in
reduced mass as well as relative velocity.

Homework Equations

KE=1/2mv^2
Momentum conservation.
Reduced mass=m1*m2/(m2-m1)

The Attempt at a Solution

So far all I've managed to come up with is the final velocity which is (m1v1+m2v2_/(m1+m2)
I'm not sure where to go form here, I've tried writing out the KE after the collision by squaring the final velocity but I can't find a place to go from here.

 

[Simon Bridge]

What is the total kinetic energy before the collision?
What is the total kinetic energy after the collision?

Do you know how to relate the velocities and masses to the relative velocity and reduced mass?