∫(√x+1)/x^2 dx=∫x^(-3/2)dx+∫dx/x^2=-2(x^(-1/2))-(1/x)代入上下限求值结果是（5-2根号2）/2
分成两个积分∫[1,2](√x+1)/x^2 dx =∫[1,2]x^(-3/2) dx+ ∫[1,2](1/x^2) dx =[-2*x^(-1/2)-1/x][1,2]=- √2-1/2+2+1= 5/2-√2
