已知x+y=m,xy=n,则(x-y)^2=?x^2+y^2=?

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已知x+y=m,xy=n,则(x-y)^2=?x^2+y^2=?
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已知x+y=m,xy=n,则(x-y)^2=?x^2+y^2=?
已知x+y=m,xy=n,则(x-y)^2=?x^2+y^2=?

已知x+y=m,xy=n,则(x-y)^2=?x^2+y^2=?
(x-y)^2=(x+y)^2-4xy=m^2-4n
x^2+y^2=(x+y)^2-2xy=m^2-2n

(x-y)^2=(x+y)^2-4xy=m^2-4n
x^2+y^2=(x+y)^2-2xy=m^2-2n