∫1/[x(x^5+4)] dx
=¼ ∫[(x^5+4)-x^5]/[x(x^5+4)] dx
=¼ ∫ [1/x-x^4/(x^5+4) ] dx
=¼[ ∫ 1/x dx-1/5 ∫ 1/(x^5+4) d(x^5+4)]
=¼ [ln|x|-1/5 ln|x^5+4|]+C
=¼ ln|x|-1/20 ln|x^5+4|+C