Question

A circle passes through point (-2, -1) and its center is at (2, -1). Which equation represents the circle?

Answer 1

Answer:

  $\text{A)}\qquad (x-2)^2+(y+1)^2=16$

Step-by-step explanation:

The formula for a circle of radius r centered at (h, k) is ...

  (x -h)^2 +(y -k)^2 = r^2

Both of the given points are on the line y=-1. The distance between them is the difference of their x-coordinates, 2 -(-2) = 4. So, the radius of the circle is 4 and the equation becomes ...

  (x -2)^2 +(y -(-1))^2 = 4^2

  (x -2)^2 +(y +1)^2 = 16 . . . . . . . . . matches choice A