tìm giới hạn:

H

hien_vuthithanh

2.$$\lim\limits_{x\to 2}\dfrac{\sqrt{x+2}+\sqrt{x+7}-5}{x-2}$$
$$=\lim\limits_{x\to 2}\dfrac{(\sqrt{x+2}-2)+(\sqrt{x+7}-3)}{x-2}$$
$$=\lim\limits_{x\to 2}\dfrac{\dfrac{x-2}{\sqrt{x+2}+2}+\dfrac{x-2}{\sqrt{x+7}+3}}{x-2}$$
$$=\lim\limits_{x\to 2}(\dfrac{1}{\sqrt{x+2}+2}+\dfrac{1}{\sqrt{x+7}+3})=\dfrac{5}{12}$$
 
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