How can I write the following equation as a first-order vector differential equation?

$\begin{array}{r}m\frac{{\mathrm{d}}^{2}x}{{\mathrm{d}}^{2}t}+2\gamma m\frac{\mathrm{d}x}{\mathrm{d}t}+kx=0.\end{array}$

$\begin{array}{r}m\frac{{\mathrm{d}}^{2}x}{{\mathrm{d}}^{2}t}+2\gamma m\frac{\mathrm{d}x}{\mathrm{d}t}+kx=0.\end{array}$