∫ axln(b/x) dx =(a/2) ∫ ln(b/x) dx^2 =(a/2)[ x^2.ln(b/x) + ∫ (b/ x^2) ( x^2/(b/x)) dx ] =(a/2)[ x^2.ln(b/x) +∫ x dx ] =(a/2)[ x^2.ln(b/x) - x^2/2 ] + C
