解
5(m-n)³+20(n-m)^5
=5(m-n)³-20(m-n)^5
=5(m-n)³[1-4(m-n)²]
=5(m-n)³[1+2(m-n)][1-2(m-n)]
=5(m-n)³(2m-2n+1)(2n-2m+1)