lim x->0+ (2x + 7 căn x)/(5x - căn x) bằng: dương vô cùng; 2/5

* Hướng dẫn giải

Chọn C

$$\begin{gathered} \underset{x\to 0^{+}}{\lim }\frac{2x+7\sqrt{x}}{5x-\sqrt{x}}=\underset{x\to 0^{+}}{\lim }\frac{\sqrt{x}\left(2\sqrt{x}+7\right)}{\sqrt{x}\left(5\sqrt{x}-1\right)} \\ =\underset{x\to 0^{+}}{\lim }\frac{\left(2\sqrt{x}+7\right)}{\left(5\sqrt{x}-1\right)}=\frac{2.0+7}{5.0- 1} =-7 \end{gathered}$$