解
x²(a+b)-a-b
=x²(a+b)-(a+b)
=(a+b)(x²-1)
=(a+b)(x-1)(x+1)
6a(m-n)²-8(n-m)³
=6a(n-m)²-8(n-m)³
=2(n-m)²[3a-4(n-m)]
=2(n-m)²(3a-4n+4m)