Trivial Question Involving Factorization (again) :)

[ManyNames]

1. The problem statement, all variables and given/known data

Factorize (E+M)(E+M) - as in E for energy and M for Mass

2. Relevant equations

.... n/a

3. The attempt at a solution

E^2+2ME+M^2

Thanks...

[ManyNames]

I know how to factorize with ordinary concordance (x^2+3x+2) which simply would be (x+2)(x+1) which is normal. However, its weird doing this with these variables, or constants, depending.