-3(x2-xy)-x(-2y+2x) ⑵ (-x5)•x3n-1+x3n•(-x)4 2. (x+2)(y+3)-(x+1)(y-2) ⑷ (-2m2n)3•mn+(-7m7n12)0-2(mn)-4•m11•n8 3. (5x2y3-4x3y2+6x)÷6x,其中x=-2,y=2 ⑹ (3mn+1)(3mn-1)-(3mn...