Solution
= Solution
Rationalizing avoids cancellation between the two large terms of the <sequence>:
$$
a_n=\frac{n}{n+\sqrt{n^2-n}}=\frac1{1+\sqrt{1-1/n}}.
$$
By <continuity> of the square root and the reciprocal at the limiting values,
$$
\boxed{\lim_{n\to\infty}a_n=\frac12.}
$$