√x/（√x-1 ）
令t=√x,dx=2tdt则x=4时t=2,x=9时,t=3
原式=∫（在上9 ,在下 4）√x/√x-1 dx
=∫[4,9] (1+ 1/(√x -1))dx
=∫[2,3] t/(t-1) *2tdt
=2∫[2,3] [t+1 +1/(t-1)] dt
=...
计算：定积分∫（在上9 ,在下 4）√x/√x-1 ..
√x/（√x-1 ）
令t=√x,dx=2tdt则x=4时t=2,x=9时,t=3
原式=∫（在上9 ,在下 4）√x/√x-1 dx
=∫[4,9] (1+ 1/(√x -1))dx
=∫[2,3] t/(t-1) *2tdt
=2∫[2,3] [t+1 +1/(t-1)] dt
=...