已知（x+2)²+|x+y+5|=0,求3x²y+{-2xy-[-2xy+(x²y-4x²)]-xy}的值 5
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解：∵（x+2)²+|x+y+5|=0
∴（x+2)²=0，|x+y+5|=0
∴x+2=0，x+y+5=0
∴x=-2，y=-3
∴3x²y+{-2xy-[-2xy+(x²y-4x²)]-xy}
=3x²y+[-2xy-(-2xy+x²y-4x²)-xy]
=3x²y+(-2xy+2xy-x²y+4x²-xy)
=3x²y+(-x²y+4x²-xy)
=3x²y-x²y+4x²-xy
=2x²y+4x²-xy
=2×(-2)²×(-3)+4×(-2)²-(-2)×(-3)
=-24+16-6
=-14
∴（x+2)²=0，|x+y+5|=0
∴x+2=0，x+y+5=0
∴x=-2，y=-3
∴3x²y+{-2xy-[-2xy+(x²y-4x²)]-xy}
=3x²y+[-2xy-(-2xy+x²y-4x²)-xy]
=3x²y+(-2xy+2xy-x²y+4x²-xy)
=3x²y+(-x²y+4x²-xy)
=3x²y-x²y+4x²-xy
=2x²y+4x²-xy
=2×(-2)²×(-3)+4×(-2)²-(-2)×(-3)
=-24+16-6
=-14
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