Which of the following functions is not injective ?

$$\begin{gathered} g\left(x\right)=x+\frac{1}{x},x\in (0,\mathrm{\infty }) \\ \frac{1}{2}, 2 \in (0,\mathrm{\infty }) \\ g\left(2\right)=2+\frac{1}{2}=\frac{5}{2} \\ g\left(\frac{1}{2}\right)=\frac{1}{2}+2=\frac{5}{2} \\ 2, \frac{1}{2} have same image \\ fis not one-one \end{gathered}$$