问题 选择题

把x2-2xy+y2-2x+2y的二次项放在添“+”号的括号里,把一次项放在添“-”号的括号里,按上述要求完成并正确的是[ ]

A. x2-2xy+y2-2x+2y=(x2+y2)-(2xy+2x-2y)

B. x2-2xy+y2-2x+2y=(x2-2xy+y2)-(2x-2y)

C. x2-2xy+y2-2x+2y=(x2+y2)-(-2xy-2x+2y)

D. x2-2xy+y2-2x+2y=(x2-2xy+y2)-(-2x+2y)

答案

答案:B

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