3(x²-2y-xy)-[3x²-2y-2(xy+y)],其中x=-1/2,y=-3_数学解答

3(x²-2y-xy)-[3x²-2y-2(xy+y)],其中x=-1/2,y=-3

人气：140 ℃　时间：2019-10-10 06:24:26

解答

3(x²-2y-xy)-[3x²-2y-2(xy+y)]
=3x²-6y-3xy-(3x²-2y-2xy-2y)
=3x²-6y-3xy-3xy+4y+2xy
=-y-xy
=3-1/2x3
=3-1.5
=1.5