\(x+\frac{1}{x}=3\)\(\Leftrightarrow\frac{x^2}{x}+\frac{1}{x}=3\)
\(\Leftrightarrow\frac{x^2+1}{x}=3\)\(\Leftrightarrow x^2+1=3x\)
\(\Leftrightarrow x^2-3x+1=0\)
\(\Delta=\left(-3\right)^2-4\left(1.1\right)=5\)
\(\Rightarrow x_{1,2}=\frac{3\pm\sqrt{5}}{2}\)