Question

(m+n)²(m-n)²-（2m+n）²（2m-n）²

Answer 1

平方差公式。
原式=[（m²-n²)+(4m²-n²)][（m²-n²)-(4m²-n²)]=(5m²-2n²)(-3m²)=6m²n²-15m^4

Answer 2

(m+n)²(m-n)²-(2m+n)²(2m-n)²
=[(m+n)(m-n)]²-[(2m+n)(2m-n)]²
=(m²-n²)²-(4m²-n²)²
=[(m²-n²)+(4m²-n²)][(m²-n²)-(4m²-n²)]
=(5m²-2n²)(-3m²)
=6m²n²-15m的4次方