已知（x+2）²+|x+y+5|=0,求3x²y+{-2x²y-[-2xy+（x²

来源：学生作业帮编辑：作业帮分类：数学作业时间：2024/10/01 09:01:05

已知（x+2）²+|x+y+5|=0,求3x²y+{-2x²y-[-2xy+（x²y-4x²）]-xy}的值

x+2=0 x=-2
x+y+5=0 3+y=0 y=-3
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}
=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+4×(-2)^2=6+16=22

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