1- lnx = (x - lnx) - x ( 1 - 1/x) 凑微分∫[ (1-lnx) /(x-lnx)^2 ] dx = x /(x - lnx) + C
>> int('(1-log(x))/(x-log(x))^2',x) ans = x/(x - log(x))所以不定积分=x/(x - log(x))+C
