Problem 12 - Entrance Test

What is the equation of the circle with center (-2, 1) and radius 3?

A. (x + 2)^2 + (y - 1)^2 = 9B. (x - 2)^2 + (y + 1)^2 = 9C. (x - 2)^2 + (y - 1)^2 = 3D. (x + 2)^2 + (y - 1)^2 = 3

Correct: A

The general equation of a circle is (x - h)^2 + (y - k)^2 = r^2, where (h, k) is the center and r is the radius. Given the center (-2, 1) and radius 3, we can plug in the values, remembering to adjust for the negative sign in the center: (x - (-2))^2 + (y - 1)^2 = 3^2, (x + 2)^2 + (y - 1)^2 = 9.