(x+y)(-x-y)的计算结果是( )A.-x2-y2B.-x2+y2C.-x2+2xy+y2D.-x2-2xy-y2
题型:单选题难度:一般来源:不详
(x+y)(-x-y)的计算结果是( )A.-x2-y2 | B.-x2+y2 | C.-x2+2xy+y2 | D.-x2-2xy-y2 |
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答案
(x+y)(-x-y), =-(x+y)2, =-(x2+2xy+y2), =-x2-2xy-y2. 故选D. |
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