Đáp án:
Giải thích các bước giải:
$\dfrac{1}{\sqrt[]{a}}+\dfrac{1}{\sqrt[]{b}}+\dfrac{1}{\sqrt[]{c}}=2\\
\rightarrow (\dfrac{1}{\sqrt[]{a}}+\dfrac{1}{\sqrt[]{b}}+\dfrac{1}{\sqrt[]{c}})^{2}=4\\
\rightarrow (\dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c})+(\dfrac{2}{\sqrt[]{ab}}+\dfrac{2}{\sqrt[]{bc}}+\dfrac{2}{\sqrt[]{ca}})=4\\
\rightarrow (\dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c})+2.(\dfrac{\sqrt[]{a}+\sqrt[]{b}+\sqrt[]{c}}{\sqrt[]{abc}})=4\\
\rightarrow \dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c}+2.1=4\\
\rightarrow \dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c}=2$
