彐M,使得ax≤M(n=012,) x n ax=n 0 =a. 0 ≤M 0 0 当<时,等比级数∑M收敛 0 0 o ∑a,x"枚敛,即级数∑anx收敛 =0 0( 0,1,2, ) a x0  M n =  n 使得 n  M, n n n n n n x x a x a x 0 0 =  n n n x x a x 0 0 =  n x x M 0  1 , 0 当  时 x x  , 0 0 等比级数 收敛 n n x x  M  = , 0  收敛  =  n n an x ; 0 即级数 收敛  n= n an x