Write the equation of the circle centered at ( 1 , − 5 ) with radius 18.

Question

Write the equation of the circle centered at  with radius 18.

Answer 1

If you recall the equation of a circle: (x-x₁)²+(y-y₁)²=r², the x₁ and y₁ values are the location of the center of your circle, and r is the radius.

Answer 2

The general equation of a circle is r² = (x-h)² + (y-k)²

R is the radius

(h,k) is the center

The center given in the problem is ( 1, -5 ) where h = 1 and k = -5 and r = 18

So filling out our equation:

18² = (x - 1)² + (y - (-5))² --> 18² = (x - 1)² + (x + 5)²

(x - 1)² + (y + 5)² = 324

Answer 3

(x-1)^2 + (y+5)^2 = 18^2

general form of the circle's equation is

(x-h)^2 + (y-k)^2 = r^2 where (h,k) is the center and r=radius