1. The problem statement, all variables and given/known data Find the equation of the circle which touches the axes and whose centre lies on the line x-2y=3 2. Relevant equations 3. The attempt at a solution The given line passes through 1st, 3rd and 4th quadrants. So the centre of the circle may lie in any of these i.e. it can be of the form (a,a) (a,-a) (-a,-a). But my book considers only (a,a) (a,-a) for finding the equation of circles.