数学题​(2x-y)²-4(x+y)(x-2y)

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数学题​(2x-y)²-4(x+y)(x-2y)
数学题​(2x-y)²-4(x+y)(x-2y)

数学题​(2x-y)²-4(x+y)(x-2y)
(2x-y)²-4(x+y)(x-2y)=4x²-4xy+y²-4(x²-xy-2y²)=9y²