Question

The equation of a a circle is (x+3)^2 + (y-5)^2 = 81. Determine the coordinates of the center of the circle && the length of the circle

A. center = (-3,5) radius = 9
B. center = (3,5) radius = 9
C. center = (-5,3) radius = 81
D. center = (5,3) radius = 81

Answer 1

In the general equation of circle,
(x - a)² + (y - b)² = r²

Centre = (a, b)
Radius = r


(x + 3)² + (y - 5)² = 81
(x + 3)² + (y - 5)² = (9)²

Comparing with general equation,
Centre = (-3, 5)
Radius = 9