已知x(x-1)-(x^2-y)=-3,求(2分之x^2+y^2)-xy的值

已知x(x-1)-(x^2-y)=-3,求(2分之x^2+y^2)-xy的值
已知x(x-1)-(x^2-y)=-3,求(2分之x^2+y^2)-xy的值

已知x(x-1)-(x^2-y)=-3,求(2分之x^2+y^2)-xy的值
x(x-1)-(x^2-y)=-3
x ^2x-x-x^2+y=-3
-x+y=-3
x-y=3
原式=(x^2-2xy+y^2)/2
=(x-y)^2/2
=9/2

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