Question

一道高数题追加50分？

求解这道题为什么发散呢，怎么判断

Answer 1

∫<0, +∞>dx/[1+e^(-x)] = ∫<0, +∞>e^xdx/(e^x+1)
= ∫<0, +∞>d(e^x+1)/(e^x+1) = [ln(e^x+1)]<0, +∞> = +∞