急求一道初中代数证明题的解体方法过程，真的不会作了帮帮忙！高分！

∵m^5+3m^4n-5m^3n^2-15m^2n^3+4mn^4+12n^5 =(m^5-5m^3n^2)+(3m^4n -15m^2n^3)+(4mn^4+12n^5) =m^3(m^2-5n^2)+3m^2n(m^2-5n^2)+4n^4(m+3n)=33 =m^2 (m^2-5n^2)(m+3n)+4n^4(m+3n) =(m+3n){m^2(m^2-5n^2)+4n^4} =(m+3n)(m^2-n^2)(m^2-4n^2) =(m+3n)(m-n) (m+n) (m-2