\(\lim_{x \to \infty} \left( \sqrt{x^2+1}-\sqrt{x^2-1} \right)\)

\(\lim_{x \to \infty} \left( \sqrt{x^2+1}-\sqrt{x^2-3x} \right)\)

\(\lim_{x \to -\infty} \frac{1+5x}{\sqrt{x^2+3}+\sqrt{2x^2-7x}}\)