18: You should get
If you decided to get rid of the square root, you should have got
This fraction is obviously of the type "infinity over infinity" (note that
thanks to the addition in the denominator, there is no trouble when putting
together the root and the x), but experience shows that
applying the l'Hospital rule to expressions with roots is seldom wise.
Fortunately, this expression can be also fitted to the box
"polynomials and ratios with
powers". We determined that the inside root behaves like
x2 when x grows large, so this is the order of the
numerator. In the denominator, the large roots term was found to behave
like x, which is the same order as the term
Obviously, the first solution is a bit simpler.