[x(x2y2-xy)-y(x2-x3y)]÷x2y
=[x2y(xy-1)+x2y(xy-1)]÷x2y
=2x2y(xy-1)/x2y
=2(xy-1)
=2xy-2
m2=n+2,n2=m+2
m2-n2=-(m-n)
(m-n)(m+n+1)=0
m≠n,m+n+1=0
,m+n= -1
m2+n2+2mn=1,m2+n2=m+2+n+2=3
mn= -1
m3-2mn+n3=(m+n)(m2-mn+n2)-2mn
=(m+n)(n+2-mn+m+2)-2mn
= -(3-mn)-2mn=-3-mn= -3+1= -2
原式=(x³y²-x²y-x²y+x³y²)÷x²y
=(2x³y²-2x²y)÷x²y
=2xy-2
14、=2（xy-1）
15、=2（m+n)
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