I know that
$(a+b)^2=a^2+b^2+2ab$ and $(a+b)^3=a^3+b^3+3ab(a+b)$
So i think it must be a formula that describes $(a+b)^n$, but I don't know what.
I know that
$(a+b)^2=a^2+b^2+2ab$ and $(a+b)^3=a^3+b^3+3ab(a+b)$
So i think it must be a formula that describes $(a+b)^n$, but I don't know what.
Use the Binomial Theorem: