1.2(x-y)^2[-2(x-y)^n]
=-4(x-y)^(2+n);
2.-6x^2y乘(a-b)^3乘1/3xy^2乘(b-a)^2
=-2x^(2+1)y^(1+2)(a-b)^(3+2)
=-2x^3y^3(a-b)^5.