其次,在圆环域:0<z-11内也可以展开为级数: f(z) (1-z)1-z1-(1-z) 1+(1-z)+(1-z)2+…+(1-z)+…] =(1-z)+1+(1-z)+(1-z) +(1-2)+10 其次,在圆环域:0<|z-1|<1内也可以展开为级数:      + - + = - + + - + - + + - + - + + - + - =       - - - = - = - - 1 1 2 2 (1 ) (1 ) 1 (1 ) (1 ) [1 (1 ) (1 ) (1 ) ] 1 1 1 (1 ) 1 1 1 (1 ) 1 ( ) n n z z z z z z z z z z z z f z