(9)y=(l+x arctan (10)y=; (11)y=xe (12)y=ln(x+√1+x2) 2.设f(x)=(x+10),f"(2)=? 3.若∫"(x)存在,求下列函数y的二阶导数}: (1)≠=f(x2); (2)y=Inlf(r)