已知x^2-xy=8,xy-y^2=3,求代数式x^2-y^2和x^-2xy+y^2的值

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已知x^2-xy=8,xy-y^2=3,求代数式x^2-y^2和x^-2xy+y^2的值
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已知x^2-xy=8,xy-y^2=3,求代数式x^2-y^2和x^-2xy+y^2的值
已知x^2-xy=8,xy-y^2=3,求代数式x^2-y^2和x^-2xy+y^2的值

已知x^2-xy=8,xy-y^2=3,求代数式x^2-y^2和x^-2xy+y^2的值
=8……(1)
=3……(2)
(1)+(2)=x^2-xy+xy-y^2=x^2-y^2=11
(1)-(2)=x^-2xy+y^2=x^2-xy-(xy-y^2)=x^2-xy-xy+y^2=5

x^2-y^2
=(x^2-xy)+(xy-y^2)
=8+3
=11
x^-2xy+y^2
=(x^2-xy)-(xy-y^2)
=8-3
=5