By completing the square, show that the following equations represent a circle and find its radius and center. (a) x2 + y2 + 2x - 6y + 7 = 0 (b) x2 + y2 - 4x + 10y + 13 = 0 (c) 16x2 + 16y2 + 8x + 32y + 1 = 0
HINT:
The general equation for a circle is (x - h)2 + (y - k)2 = r2, where r is the radius and (h, k) is the center.