题目内容
若(2x-5y)2=(2x+5y)2+m,则代数式m为( )
| A.-20xy | B.20xy | C.40xy | D.-40xy |
(2x-5y)2=(2x+5y)2+m,
整理得:4x2-20xy+25y2=4x2+20xy+25y2+m,
∴-20xy=20xy+m,
则m=-40xy.
故选D
整理得:4x2-20xy+25y2=4x2+20xy+25y2+m,
∴-20xy=20xy+m,
则m=-40xy.
故选D
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