ln(1+x)=x--x2 23 +o(x"); (1+x)2=1+x+(c-1) ala (a-n+1) +0(x 特别 =1+x+x2+…+x"+o(x") 下1 1 1 2 3 ( 1) ln(1 ) ( ); 2 3 n n n x x x x x o x n − − + = − + −"+ + 2 ( 1) ( 1) ( 1) (1 ) 1 2! ! ( ); n n n x x x x n o x α α α α α α α − − − + + = + + + + + " " 1 2 1 ( ). 1 n n x x x o x x = + + + + + − " 特别