The equations of the directrix of the parabola with vertex at the origin and having the axis along the x-axis and a common tangent of slope 2 with the circle x² + y² = 5 is
(are)

The line y =2x+ c is a tangent to x² + y² = 5'
lf c² = 25, then c =$\pm 5$
Let the equation of the parabola be y² - 4ax. Then.
$\frac{\mathrm{a}}{2}=\pm 5$
or  $\mathrm{a}=\pm 10$
So, the equation of the parabola is ${\mathrm{y}}^2=\pm 40\mathrm{x}$
Also, the equations of the directrices are $\mathrm{x}=\pm 10.$