Hard M2 question

A sphere of mass m1 moving with speed u1 collides directly with a similar sphere of mass m2 moving with speed u2 in the same direction (u1>u2). The coefficient of restitution between the two spheres is e. Show that the loss of kinetic energy E due to the collision satisfies the equation

2(m1 + m2)E = m1m2(1-e^2)(u1 - u2)^2

Is this the one from the heinemann book?
It's been done before and the working involved is quite tedious! I think a solution has been posted somewhere in a past thread.

use:

e=(v2-v1)/(u1-u2)

where v2 and v1 are the speeds of m2 and m1 after the collision respectively, to work out v2 and v1 in terms of e, u1 and u2