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x² + 20x + y² + 16y = -20

The equation above defines a circle in the xy-plane. What are the coordinates of the center of the circle?

Point O is the center of the circle above, and the measure of ∠OAB is 30°. If the length of \( OC \)  is 18, what is the length of arc \( AB \) ?

A circle in the xy-plane has a diameter with endpoints 2, 4 and 2, 14. An equation of this circle is \( \left(x-2\right)^2+\left(y-9\right)^2=r^2 \) , where r  is a positive constant. What is the value of r ?

Circle A in the xy-plane has the equation (x + 5)² + (y - 5)² = 4. Circle B has the same center as circle A. The radius of circle B is two times the radius of circle A. The equation defining circle B in the xy-plane is (x + 5)² +(y - 5)² = k, where k is a constant. What is the value of k?

What is the diameter of the circle in the xy-plane with equation \( \left(x-5\right)^2+\left(y-3\right)^2=16 \)  ?

The equation (x + 6)² + (y + 3)² =121 defines a circle in the xy‑plane. What is the radius of the circle?

A circle has a radius of 43 meters. What is the area, in square meters, of the circle?

Circle A has a radius of 3n and circle B has a radius of 129n, where n is a positive constant. The area of circle B is how many times the area of circle A?

A circle in the xy-plane has a diameter with endpoints (2, 4) and (2, 14) . An equation of this circle is (x −2)²+(y −9)²= r², where r is a positive constant. What is the value of r ?

The circle shown has center O, circumference 144π, and diameters \( PR \)   and \( QS \)  . The length of arc PS is twice the length of arc PQ. What is the length of arc QR?

The length of a side of square X is 9 centimeters. The area of rectangle Y is 24 square centimeters. What is the total area, in square centimeters, of square X and rectangle Y?

A total of 2 equilateral pentagons each have side length p units. A total of 6 squares each have side length s units. The sum of the perimeters of all these pentagons and squares is 116 units. Which equation represents this situation?