5) $\lim _{x \rightarrow \infty} \sqrt{x^{2}+2 x}-\sqrt{x^{2}-8 x}$
So, the final answer is \(\boxed{5}\).
Step 1 :Given the expression \(\sqrt{x^{2}+2 x}-\sqrt{x^{2}-8 x}\), we are asked to find the limit as x approaches infinity.
Step 2 :We can simplify the expression by multiplying and dividing by the conjugate. This will allow us to cancel out terms and simplify the expression to a form that we can easily evaluate the limit of.
Step 3 :Let's rewrite the expression as \(-\sqrt{x(x - 8)} + \sqrt{x(x + 2)}\).
Step 4 :By evaluating the limit of this expression as x approaches infinity, we find that the limit is 5.
Step 5 :So, the final answer is \(\boxed{5}\).