题目

已知 x﹣y＝4，|x|+|y|＝7，那么 x+y 的值是（ ）A. ± B. ± C. ±7 D. ±1 答案：【答案】C【解析】根据x-y=4，可得：x=y+4，代入|x|+|y|=7，然后分类讨论y的取值即可。解：由x-y=4，得：x=y+4，代入|x|+|y|=7，∴|y+4|+|y|=7，①当y≥0时，原式可化为：2y+4=7，解得：y=，②当y≤-4时，原式可化为：-y-4-y=7，解得：y=−，③当-4＜y＜0时，原式可化为：y+4-y=7，故此时无解；所以当y=时，x=，x+y=7，当The manager asked him if he ________for the extra work the next weekend.A. had come B. will come C.would come D. came