What is the general form of the equation of a circle with center at (a, b) and radius of length m? a. x2 + y2 ? 2ax ? 2by + (a2 + b2 ? m2) = 0 b. x2 + y2 + 2ax + 2by + (a2 + b2 ? m2) = 0 c. x2 + y2 ? 2ax ? 2by + (a + b ? m2) = 0 d. x2 + y2 + 2ax + 2by + a2 + b2 = -m2