化简:①-1/2x-(x-3)②-1/2(4x-6)+1/3(6-3x)③-(x²-2x-2)+2(x²-1)④2n-(2-n)+(6n-2)

问题描述:

化简:①-1/2x-(x-3)②-1/2(4x-6)+1/3(6-3x)③-(x²-2x-2)+2(x²-1)④2n-(2-n)+(6n-2)
化简并求值:(a²b-ab)-2(ab²-ba),其中a=-1/2,b=2

原式=ab(1+a-2b)=7/2