已知X+Y=1,XY=-12,求X^2+Y^2的值
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已知X+Y=1,XY=-12,求X^2+Y^2的值
已知X+Y=1,XY=-12,求X^2+Y^2的值
已知X+Y=1,XY=-12,求X^2+Y^2的值
X^2+Y^2=(X+Y)^2-2XY=1+24=2 5
25
X^2+Y^2=(X+Y)^2-2XY=1+24=25
X^2+Y^2=(X+Y)^2-2xy=1-2(-12)=25
X^2+Y^2=(X+Y)^2-2XY
=1+24
=25
(x+y)^2-2xy 带入数据即可
X+Y=1
(X+Y)^2=1
X^2+2XY+Y^2=1
已知:XY=-12
X^2+Y^2=1+2*12=25
(x+y)^2 = 1 , x^2 + 2xy + y^2 = 1,x^2 + y^2 = 1-2xy = 25
X+Y=1,XY=-12
(X+Y)^2=1,
X^2+Y^2+2xy=1,
X^2+Y^2=-2xy+1=-2(-12)+1=25