Can someone help me solve this problem?

Question

Multiply, using the vertical method. (m + 3n)(m^2 - 3mn + 9n^2)

Answer 1

Simply Multiply m by the secnd pranteses , then Multiply 3n to the second pranteses then add these two :

(m+3n)(m^2-3mn+9n^2) =
m^3+3m^2n+9m.n^2+3n.m^2-9m.n^2+18n^3 =
m^3+3m^2.n+3n.m^2+18n^3

Answer 2

m^2+9n^2m+3nm^2-m

That's my guess but I'm not totally sure.
Sorry!