1.(a-b)(a²-ab+b²)-ab(b-a)
=(a-b)(a²-ab+b²)+ab(a-b)
=(a-b)(a²-ab+b²+ab)
=(a-b)(a²+b²)
2.(7a-8b)(a-2b)+(a-8b)(a-2b)
=(a-2b)[(7a-8b)+(a-8b)]
=(a-2b)(8a-16b)
=8(a-2b)²
3.x²-xy-2y²
=(x+y)(x-2y)
4.(m-n)²-(m-n)-12
=[(m-n)+3][(m-n)-4]
=(m-n+3)(m-n-4)
5.-2a五次方b平方+8a四次方b-8a三次方
=-2a^3(a²b²-4ab+4)
=-2a^3(ab-2)²