Distance formula:




What is the radius of a circle whose equation is x2+y2+8x−6y+21=0?
What is the center of a circle whose equation is x2 + y2 – 12x – 2y + 12 = 0?
On a coordinate plane, a circle has a center at (1, negative 2) and a radius of 4 units.

Which equation represents a circle with a center at (–3, –5) and a radius of 6 units?
In the diagram, a circle centered at the origin, a right triangle, and the Pythagorean theorem are used to derive the equation of a circle, x2 + y2 = r2.
What is the center of a circle whose equation is x2 + y2 + 4x – 8y + 11 = 0?
Which equation represents a circle that contains the point (–5, –3) and has a center at (–2, 1)? Distance formula:

Which equation represents a circle that contains the point (–2, 8) and has a center at (4, 0)?Distance formula:

Which equations represent circles that have a diameter of 12 units and a center that lies on the y-axis? Select two options.x2 + (y – 3)2 = 36x2 + (y – 5)2 = 6(x – 4)² + y² = 36(x + 6)² + y² = 144x2 + (y + 8)2 = 36
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