(2x-y)^2-4(x-y)(x+2y) (2x-y)^2-4(x-y)(x+2y)

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(2x-y)^2-4(x-y)(x+2y) (2x-y)^2-4(x-y)(x+2y)

(2x-y)^2-4(x-y)(x+2y) (2x-y)^2-4(x-y)(x+2y)
(2x-y)^2-4(x-y)(x+2y)
(2x-y)^2-4(x-y)(x+2y)

(2x-y)^2-4(x-y)(x+2y) (2x-y)^2-4(x-y)(x+2y)
(2x-y)^2-4(x-y)(x+2y)
=4x^2-4xy+y^2-4(x^2+2xy-xy-2y^2)
=4x^2-4xy+y^2-4x^2-4xy+8y^2
=9y^2-8xy.

(2x-y)^2-4(x-y)(x+2y)
=4x^2-4xy+y^2-4x^2-8xy+4xy+8y^2
=9y^2-8xy

(2x-y)^2-4(x-y)(x+2y)
=4x^2-y^2-4(x^2+2xy-xy-2y^2)
=4x^2-y^2-4x^2-8xy+4xy+8y^2
=9y^2-4xy