Let y be a function of x. Which of the following is a first order linear differential equation?

$1.{y}^{\prime}-x={y}^{2}\mathrm{sin}\left(x\right)$

$2.{y}^{\prime}-x=y\mathrm{sin}\left(x\right)$

$3.{\left({y}^{\prime}\right)}^{2}+y=\mathrm{tan}\left(2x\right)$

$4.{y}^{\prime}={y}^{2}{e}^{x}$

$5.{\left({y}^{\prime}\right)}^{2}+y={e}^{x}$