Rob2233 发表于 2017-2-23 21:45- E2 T. b- T' E" `5 z: b) G
如果觉得难度不够的话,可以试试加拿大公开赛(Canadian Open Mathematics Challenge)的题, : `$ L2 } M4 x) S( |这应该是比 ...
8 C, ]) t( V/ m: p X' y1 sthanks a lot as parents, but i guess my daughter going to hate you. i won't let her know who you are. please keep sending this kind good resource for all parents.