Equation of Circles

This lessson is part of a series of lessons for the quantitative reasoning section of the GRE revised General Test. In this lesson, we will learn how to graph and write the equations of circle.

Equation of a Circle

The graph of an equation of the form (x − a)² + (y − b)² = r² is a circle with its center at the point (a, b) and with radius r.

This video looks at using equations of circles to find the center and the radius of a circle to graph it, as well as, writing an equation for a circle, given the center and radius, or a point on the circle. It includes four examples.

This video shows how to graph and write equations of circles.

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