已知A=x²-2xy+y,B=x²+2xy+y²-3,求2A-[B-(B-A)+2A+B] 急._数学解答

已知A=x²-2xy+y,B=x²+2xy+y²-3,求2A-[B-(B-A)+2A+B] 急.

人气：256 ℃　时间：2020-10-02 03:48:13

解答

解2A-[B-(B-A)+2A+B]=2A-[B-B+A+2A+B]=2A-(B+3A)=-B-A=-(x²+2xy+y²-3)-(x²-2xy+y)=-x²-2xy-y²+3-x²+2xy-y=(-x²-x²)+(2xy-2xy)-y²-y+3=-2x²-y²-y+3