UPSC NDA I 2015 Mathematics Solved Paper

For any point on the parabola y2=4ax, the distance from the focus (a, 0) is equal to the distance of the point from the directrix x=−a
For the point (0, 0), the distance from directrix is ‘a’. As all other points on the parabola are in the first quadrant, their distance from the directrix will be more than ‘a’. Hence, the distance of all these points from the focus will also be more than ‘a’. This implies (0, 0) is the point which is nearest to the focus (a, 0). Its abscissa or X-coordinate is 0.