Question #N312
A circle with center at the origin has a radius of 5. What is the equation of the circle?
A. x^2 + y^2 = 5
B. x^2 + y^2 = 25
C. (x - 5)^2 + (y - 5)^2 = 25
D. (x + 5)^2 + (y + 5)^2 = 25
Correct Answer is: B
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 circle has center at the origin (0, 0) and radius 5, the equation of the circle is (x - 0)^2 + (y - 0)^2 = 5^2, or x^2 + y^2 = 25.