Phương pháp: Hằng số vắng
Tính các giới hạn:
1, lim\frac{2\sqrt{1+x} - \sqrt[3]{8-x}}{x}
2,\mathop {\lim }\limits_{x \to 1}\frac{\sqrt[4]{2x-1} + \sqrt[5]{x-2}}{x-1}
3,\mathop {\lim }\limits_{x \to 1}\frac{2\sqrt{5-x^{3}}-\sqrt[3]{x^2 +7}}{x^2 -1}
4, \mathop {\lim }\limits_{x \to 0}\frac{(x^2+2009)\sqrt[7]{1-2x}-2009}{x}
5,\mathop {\lim }\limits_{x \to 7}\frac{\sqrt{x+2}-\sqrt[3]{x+20}}{\sqrt[4]{x+9}-2}
6, \mathop {\lim }\limits_{x \to 1}\frac{\sqrt{2x-1}+x^2-3x+1}{\sqrt[3]{x-2}+x^2-x+1}