显然xn+>xn,∴{x}是单调递增的; x.<1+1+-+…+<1+1+=+…+ =3-n1<3,:{x}是有界的; limx,存在 n→0 记为Im(+)y=e(C=271828) n→00, 显然 xn+1  xn  是单调递增的;  x n ! 1 2! 1 1 1 n xn  + + ++ 1 2 1 2 1 1 1 −  + + + +  n 1 2 1 3 − = − n  3,  是有界的;  x n lim 存在. n n x →  e n n n + = → ) 1 记为lim(1 (e = 2.71828)