Question #N6
A circle has a radius of 5 units. The point (-3,1) lies on the circle. What is the equation of the circle?
A. (x + 3)^2 + (y - 1)^2 = 25
B. (x + 3)^2 + (y - 1)^2 = 5
C. (x - 3)^2 + (y + 1)^2 = 25
D. (x - 3)^2 + (y + 1)^2 = 5
Correct Answer is: A
The standard form of the equation of a circle with center (h, k) and radius r is (x - h)^2 + (y - k)^2 = r^2. Since the center of the circle is (-3, 1) and the radius is 5, the equation of the circle is (x - (-3))^2 + (y - 1)^2 = 5^2, or (x + 3)^2 + (y - 1)^2 = 25.