Russianal Limits

Calculus Level 1

If $L=\displaystyle \lim_{x \rightarrow 0} \frac{\sqrt{x^{2} + 2014^{2}}-2014}{\sqrt{x^2+2015^{2}}-2015}$ , and $L$ can be represented in the form $\dfrac{a}{b}$ , find $a-b$ . Ensure that $a$ and $b$ are relatively prime.