∫[0,16]1/[√(x+9)-√x] dx
=1/9∫[0,16][√(x+9)+√x] dx
=1/9*[2/3(x+9)^(3/2)+2/3*x^(3/2)][0,16]
=1/9*[250/3+128/3-54/3]
=12用换元法怎么算呢？谢谢了不需要用换元法呀