use quotient rule.
where u=x v=sqrt (x squared + 1)
u'=1 v'=x/sqrt(x squared+1)
so dy/dx= [sqrt(x squared + 1)-x^2/sqrt(x squared+1)]/(x squared+1)
thats pretty messy.
dy/dx=1/sqrt (x squared + 1) - x^2/(x^2+1)^(3/2)
i think
edit:dy/dx=(x^2+1)/((x^2+1)^(3/2) - x^2/(x^2+1)^(3/2)
=1 /...