Expand (3f+2h)^4

Using the terms in Pascal's triangle and the Binomial Theorem

= (3f)^4 + 4(3f)^3(2h) + 6(3f)^2 (2h)^2 + 4(3f) (2h)^3 + (2h)^4
= 81f^4 + 216f^3 h + 216 f^2 h^2 + 96 f h^3 + 16 h^4