What is the final velocity of a bouncing ball after hitting a wall?

[imsmooth]

I've seen the solution to finding the velocity after a ball bounces off of a wall.
http://www.lhup.edu/~dsimanek/ideas/bounce.htm

If a ball of mass m1 and velocity v1 hit a massive wall, what is the final velocity. I understand the math. What I find a little confusing is reconciling the math and how the equation
m1v1 = m1v2 + MV satisfies conservation of momentum if v1 = -v2 and V = 0.

Is it that the massive wall of mass M moves will an infinitesimally small velocity such that MV balances the
-2m1v2?

 

[Orodruin]

Yes, you can see this by solving it for a finite M and then taking the limit as M goes to infinity.