What is the general form of the equation of a circle with its center at (-2, 1) and passing through (-4, 1)?
A) x2 + y2 − 4x + 2y + 1 = 0
B) x2 + y2 + 4x − 2y + 1 = 0
C) x2 + y2 + 4x − 2y + 9 = 0
D) x2 − y2 + 2x + y + 1 = 0

Question

What is the general form of the equation of a circle with its center at (-2, 1) and passing through (-4, 1)?
A) x2 + y2 − 4x + 2y + 1 = 0
B) x2 + y2 + 4x − 2y + 1 = 0 
C) x2 + y2 + 4x − 2y + 9 = 0
D) x2 − y2 + 2x + y + 1 = 0

phi · Answer

First, can you figure out the length of the radius.  It would be the distance from the center at (-2,1) to the point on the circle e.g. (-4,1)
?