Li-Fan Chen => YSITD: 1/a + 1/b - 1/ab + (1 - 1/a)(1 - 1/b) =1 剛剛才發現這件事(? #58c1585811ae01cd92ad04f4

Li-Fan Chen says to YSITD

1/a + 1/b - 1/ab + (1 - 1/a)(1 - 1/b) =1 剛剛才發現這件事(?

at Thu, Mar 9, 2017 9:27 PM