Question

On a coordinate plane, a circle has a center at (negative 2, 1).
Which is the general form of the equation of the circle shown?

x2 + y2 + 4x – 2y – 4 = 0
x2 + y2 + 4x – 2y + 2 = 0
x2 + y² – 4x + 2y – 4 = 0
x2 + y² – 4x + 2y + 2 = 0

Answer 1

Center (h,k)=(-2,1) means the equation is (x+2)^2 + (y-1)^2 = r^2.
Expanding (x+2)^2 + (y-1)^2 = 9 gives x^2 + y^2 + 4x - 2y - 4 = 0.

So the correct choice is: x^2 + y^2 + 4x – 2y – 4 = 0.