(1)(3a-3b)+6(b-a)
＝3(a-b)-6(a-b)＝-3(a-b)＝3(b-a)
(2)5x(x-3y)^2-(3x+2y)(3y-x)^2
=(5x-3x-2)(3y-x)^2 =2(x-1)(3y-x)^2