Question #N651
A circle in the xy-plane has its center at $(4,-5)$ and a radius of 7. Which of the following is an equation for this circle?
A. (x - 4)^2 + (y + 5)^2 = 49
B. (x + 4)^2 + (y - 5)^2 = 49
C. (x - 4)^2 + (y + 5)^2 = 7
D. (x + 4)^2 + (y - 5)^2 = 7
Correct Answer is: A
The standard form of the equation of a circle in the xy-plane with center (h, k) and radius r is (x - h)^2 + (y - k)^2 = r^2. Since the center of the circle is (4, -5) and the radius is 7, the equation of the circle is (x - 4)^2 + (y + 5)^2 = 7^2, or (x - 4)^2 + (y + 5)^2 = 49.