6a²-2ab-2【3a²+二分之一ab】=6a²-2ab-6a²-﹙1／10﹚ab=﹙-21／10﹚ab
3【x-1】-【x-5】,
3【x-1】-【x-5】=3x-3-x+5=2X+2,
,
把x=2.代入2X+2=2×2﹢2=6【2xy-y】-【-y+yx】；问下，这道题化简后是多少。。【2xy-y】-【-y+yx】；=2xy-y+y-yx=XY