Which of the following equations represents a circle that has a center located at (4, -2) and has a diameter of 22 units?

Question

A. (x + 4)² + (y - 2)² = 484

B. (x + 4)² + (y - 2)² = 121

C. (x - 4)² + (y + 2)² = 484

D. (x - 4)² + (y + 2)² = 121

Answer 1

c) is correct. 22 squared = 484

general equation for a circle is (x-h)^2 + (y-k)^2 =r^2 where (h,k)= the center and r= radius. IF (4,-2) = (h,k) and r=22

then the equation is (x-4)^2 + (y+2)^2 = 22^2 = 484.

a) is close but off by one sign

Answer 2

Hi Erica! Here's some advice to get you started on this question.

A circle's equation is (x−h)^2+(y−k)^2=r^2. The center of the circle is (h,k) and the radius is r.

For answer choice A, the center is (h,k)=(-4,2) and the radius is r=sqrt(484)=22. A circle with a radius of 22 would have a diameter of 44 (as the diameter is twice the radius).

Follow a similar thought process as you think through answer choices B-D! Let me know if you need more help with this problem.