例4计算下列积分 Dxdx.(2)dx.(3) dx 3 解(1)3xdx d X3 x3+ +1 4 dx +C=2x+ X (3)dx=∫x 2+1 X +O X 前页后页结束前页 后页 结束 例4 计算下列积分 d . 1 d . (3) 1 (1) d . (2) 2 3 x x x x x x    . 4 3 1 3 1 1 3 4 1 3 1 x + C = x + C + = + x x x d x d 1 (2) 2 1   − = 解 (1) xdx x3 dx 1 3   = x x x x d d 1 (3) 2  2  − = 2 . 2 1 1 1 2 1 1 x + C = x + C − = − . 1 2 1 1 2 1 C x x + C = − + − + = − +