已知x(x-1)-(x^2-y)=-3,求3x^2+3y^2-6xy的值
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已知x(x-1)-(x^2-y)=-3,求3x^2+3y^2-6xy的值
已知x(x-1)-(x^2-y)=-3,求3x^2+3y^2-6xy的值
已知x(x-1)-(x^2-y)=-3,求3x^2+3y^2-6xy的值
x(x-1)-(x^2-y)=-3
x^2-x-x^2+y=-3
-x+y=-3
x-y=3
原式=3(x^2-2xy+y^2)
=3(x-y)^2
=3×3^2
=27
前式推得y-x=-3
后式子=3(y-x)²=27
x(x-1)-(x^2-y)=-3===》-x+y=-3,y=x-3
3x^2+3y^2-6xy =3(x-y)^2=3*3^2=27
前式推得y-x=-3;x-y=3;
后式子=3(x^2-2xy+y^2)=3(x-y)^2=27
由已知可得 x^2-x-x^2+y=-3
-x+y=-3
x-y=3
原式==3(x-y)^2=27