∑an与∑bn收敛 ∑An收敛 n n n= n n 又 ∑4≤∑|4k =1 lim∑4 k slim∑|4k n→>o0k=1 n→>0k=1 ∑≤∑ n= n=n a 1 1 n n n b   = =  与 收敛 n A n 1  =  收敛 n k 1 1 n k k k A A = = 又    n k n 1 1 lim lim n k k k n A A → → = =     n 1 1 n n n A A   = =    