A line that is perpendicular to the x-axis is a vertical like with a slope equal to infinity. A line parallel to it would have the same slope and will also be a vertical line perpendicular to the x-axis. As the line passes through the point (2, -1) its equation is x = 2.

**The equation of the required line is x - 2 = 0**

Since the line is perpendicular to the x-axis, then, the line is vertical.

And if the line passes throught the point (2,-1), hence the equation is x = 2.

**Answer: Equation of the line is x=2 .**