第二題答案是不是:C(16+3,3)+C(15+3,3)+...+C(1+3,3)+C(0+3,3)
所有跟帖:
• I think we should change 16 to 20....we get C(24,4)=... -jinjing- ♀ (0 bytes) () 09/08/2010 postreply 09:35:30
• how to understand: must be invested among 4 possible opportuniti -皆兄弟也- ♂ (81 bytes) () 09/08/2010 postreply 10:00:33
• even if we should change 16 to 20....we get C(21,4)=... -皆兄弟也- ♂ (0 bytes) () 09/08/2010 postreply 10:03:46
• sorry, C(21,4)=... wrong; C(24,4)=... right,if we should change -皆兄弟也- ♂ (0 bytes) () 09/08/2010 postreply 10:07:18