写得不清楚 lny=lnx^3+lnx*ln(x^2+1)-x-x^2ln(x+1) 求导得：y'/y=3/x+ln(x^2+1)/x+lnx*(2x)/(x^2+1)-1-2xln(x+1)-x^2/(x+1) 所以：y'=y[3/x+ln(x^2+1)/x+lnx*(2x)/(x^2+1)-1-2xln(x+1)-x^2/(x+1)]
