Differential Equations

$x \frac{\mathrm{~d} y}{\mathrm{~d} x}-2 y=0$

$\frac{\mathrm{d} y}{\mathrm{~d} x}+x y=0$

$\quad x \frac{\mathrm{~d} y}{\mathrm{~d} x}+y=0$

$x^2 \frac{\mathrm{~d} y}{\mathrm{~d} x}+y=0$