令根号2x+1 =t x=（t^-1)/2 原式=∫t/((t^-1)/2 *t)dt =∫2/(t-1)(t+1) dt = -∫1/(t+1) -1/(t-1) dt =
ln((t+1)/(t-1)) +c
故原式=- ln ( (根号(2x+1) +1)/(根号(2x+1) -1) ) +c