例7求 1+e 1+e2-e 解 d x dx 1+e 1+er e dx = dx 1+e 1+e ∫4-,4(+e) x-In(1+e )+C例7 求 . 1 1 dx e  x + 解 dx e  x 1+ 1 dx e e e x x x  + + − = 1 1 dx e e x x        + = − 1 1 dx e e dx x x   + = − 1 (1 ) 1 1 x x d e e dx + + =  − x ln(1 e ) C. x = − + +