Hệ \Leftrightarrow $\left\{\begin{matrix}\dfrac{xy}{x+y}=1 & \\\dfrac{xz}{x+z}=2 & \\\dfrac{yz}{y+z}=3 &\end{matrix}\right.$
\Leftrightarrow $\left\{\begin{matrix}\dfrac{x+y}{xy}=1 & \\\dfrac{x+z}{xz}=\dfrac{1}{2} & \\\dfrac{y+z}{yz}=\dfrac{1}{3} &\end{matrix}\right.$
\Leftrightarrow $\left\{\begin{matrix}\dfrac{1}{x}+\dfrac{1}{y}=1 & \\\dfrac{1}{x}+\dfrac{1}{z}=\dfrac{1}{2} & \\\dfrac{1}{y}+\dfrac{1}{z}=\dfrac{1}{3} &\end{matrix}\right.$
Cộng theo vế 3 PT,đc:
$\dfrac{1}{x}+\dfrac{1}{y}+\dfrac{1}{z}=\dfrac{11}{12}$
\Rightarrow $\dfrac{1}{x}=\dfrac{7}{12};\dfrac{1}{y}=\dfrac{5}{12};\dfrac{1}{z}=\dfrac{-1}{12}$