m³(m-2n)+n³(2m-n) =m^4-2m³n+2mn³-n^4 =(m^4-n^4)-2mn(m²-n²) =(m²+n²)(m²-n²)-2mn(m²-n²) =(m²-n²)(m²-2mn+n²) =(m+n)(m-n)&su...