化简:(x-y)^2-y(3y-2x),其中x=根号5,y=-根号2

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化简:(x-y)^2-y(3y-2x),其中x=根号5,y=-根号2
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化简:(x-y)^2-y(3y-2x),其中x=根号5,y=-根号2
化简:(x-y)^2-y(3y-2x),其中x=根号5,y=-根号2

化简:(x-y)^2-y(3y-2x),其中x=根号5,y=-根号2
(x-y)^2-y(3y-2x)
=x^2+y^2-2xy-3y^2+2xy
=x^2-2y^2
=5-4=1

(x-y)^2-y(3y-2x)
=x^2-2xy+y^2-3y^2+2xy
=x^2-2y^2
=5-2×2
=5-4
=1

(x-y)^2-y(3y-2x)=x^2+y^2-2xy-3y^2+2xy=x^2-2y^2
x=根号5,y=-根号2
上式=5-2*2=1

(x-y)^2-y(3y-2x)
=x²-2xy+y²-3y²+2xy
=x²-2y²
=(√5)²-2×(-√2)²
=5-2×2
=5-4
=1

原式=x^2-2xy+y^2-3y^2+2xy
=x^2-2y^2
因为x=根号5,y=-根号2
所以5-4=1