例4求 (1+x) x+1-1 解 (x= (1+x)3 3 1+x) (1+x)2(1+x)3 Id(1+x) +C, +c 1+x 2(1+x) 2 + 1+x2(1+x)例4 求 . (1 ) 3 dx x x  + 解 dx x x  + 3 (1 ) dx x x  + + − = 3 (1 ) 1 1 ] (1 ) (1 ) 1 (1 ) 1 [ 2 3 d x x x + + − + =  1 2 2 2(1 ) 1 1 1 C x C x + + + + + = − . 2(1 ) 1 1 1 2 C x x + + + + = −