circle part 1 doubts

1
First of all, it bisects the circumference, so it won’t be passing through the centre but will pass through two diametric ends of the circle.
Draw a correct diagram and half the job will be done. the line joining the 2 points of intersection join to form a diameter of the second circle (Also this line passes through the centre). Subtract the 2 circle eqns to obtain the emperical eqn of the line joining its points of intersection. The line joining the centres will be perpendicular to it. From this, find the slope of line joining the 2 centres and thence, the slope of line perpendicular to it, which inturn is the line joining the points of intersection of the 2 circles. This line passes through the centre of the second circle. You have the slope of it, the coordinates of the point through which it passes. (And yes, tihs eqn does contain (c+d)) So putting the values of slope and coordinates in the eqn would leave (c+d) as the only variable which can then be calculated.