1. $\mathop {\lim }\limits_{x \to 2}$ $(x^{4} - 5x^{3} + 8x^{2} -6x +3)$
2. $\mathop {\lim }\limits_{x \to 2^{+}}$ $\sqrt{x^{3} +x^{2} -6x}$
3. $\mathop {\lim }\limits_{x \to -1}$ $\sqrt[2012]{\frac{3x^{2} - 5x + 4}{x - 2} +3x +8}$
4. $\mathop {\lim }\limits_{x \to -1}$ ($ \sqrt[4]{\frac{x}{x - 2}} + \sqrt[3]{\frac{x + 2}{x}}$)