(-3xy-7y)+[4x-3(xy+y-2x)],其中xy=-2,x-y=3,先化简,再求值.
问题描述:
(-3xy-7y)+[4x-3(xy+y-2x)],其中xy=-2,x-y=3,先化简,再求值.
答
(-3xy-7y)+[4x-3(xy+y-2x)],
=-3xy-7y+4x-3xy-3y+6x
=-6xy+10x-10y
=-6xy+10(x-y) xy=-2,x-y=3
=-6×(-2)+10×3
=18+30
=48