1. The problem statement, all variables and given/known data Well, I was trying to expand say for the third power of (A+B), where A and B are non-commutative. 3. The attempt at a solution I get [tex] (A+B)^3=(A^2+AB+BA+B^2)(A+B)=A^3+ABA+BA^2+B^2A+A^2B+AB^2+BAB+B^3[/tex] but from a few sources online, it should be [tex] (A+B)^3=(A^3+3A^2B+3AB^2+B^3)-3(AB-BA)(A+B) [/tex] Now, these 2 results don't seem to be equivalent and I have checked this by expanding it myself. I have been thinking for quite some time about what is wrong with my answer but I seem to be getting nowhere. Any help would be greatly appreciated.