已知x+y=-5,x*x+y*y=19求xy和(x-y)*(x-y)的值

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已知x+y=-5,x*x+y*y=19求xy和(x-y)*(x-y)的值已知x+y=-5,x*x+y*y=19求xy和(x-y)*(x-y)的值已知x+y=-5,x*x+y*y=19求xy和(x-y)

已知x+y=-5,x*x+y*y=19求xy和(x-y)*(x-y)的值
已知x+y=-5,x*x+y*y=19求xy和(x-y)*(x-y)的值

已知x+y=-5,x*x+y*y=19求xy和(x-y)*(x-y)的值
x²+y²=19
(x+y)²=x²+y²+2xy=25
xy=3
(x-y)*(x-y)=(x-y)²=x²+y²-2xy=13

xy={(x+y)(x+y)-(x*x+y*y)}/2=3
(x-y)*(x-y)=x*x+y*y-2xy=13