Use L'H^opital's Rule to Find the Limit $\lim _ { x \rightarrow \infty } \left( \sqrt { x ^ { 2 } + 6 x } - x \right)$

Multiple Choice

Use l'H^opital's rule to find the limit.
- $\lim _ { x \rightarrow \infty } \left( \sqrt { x ^ { 2 } + 6 x } - x \right)$

A) - 3
B) 0
C) 3
D) 6