已知（x+2）²+|x+y+5|=0,求3x²y+{-2x²y-[-2xy+（x²y-4x²）]-xy}的值
问题描述：
已知（x+2）²+|x+y+5|=0,求3x²y+{-2x²y-[-2xy+（x²y-4x²）]-xy}的值
答
x+2=0
x+y+5=0
∴x=-2
y=-3
∴原式=3x²y-2x²y+2xy-x²y+4x²-xy
=xy
=6
答
x+2=0 x=-2x+y+5=0 3+y=0 y=-33x^2y+{-2x^2y-[-2xy+（x^2y-4x^2）]-xy}=3x^2y+{-2x^2y-[-2xy+x^2y-4x^2]-xy}=3x^2y+{-2x^2y+2xy-x^2y+4x^2-xy}=3x^2y-2x^2y+2xy-x^2y+4x^2-xy=xy+4x^2把x=-2,y=-3代入xy+4x^2.-2×-3+...