(x-y)^2-(2x-y)^2 4x^2-nxy+9y^2
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![(x-y)^2-(2x-y)^2 4x^2-nxy+9y^2](/uploads/image/z/1077002-26-2.jpg?t=%28x-y%29%5E2-%282x-y%29%5E2+4x%5E2-nxy%2B9y%5E2)
(x-y)^2-(2x-y)^2 4x^2-nxy+9y^2
(x-y)^2-(2x-y)^2 4x^2-nxy+9y^2
(x-y)^2-(2x-y)^2 4x^2-nxy+9y^2
(x-y)^2-(2x-y)^2
=[(x-y)-(2x-y)][(x-y)+(2x-y)]
=(-x)(3x-2y)
=-x(3x-2y)
4x^2-nxy+9y^2 (n=12 )
4x^2-12xy+9y^2
=(2x-3y)^2
(x-y)^2-(2x-y)^2=-x(3x-2y)
4x^2-nxy+9y^2=(2x-3y)^2