Key Concepts: Equations of Circles ⭐

Standard Form

The equation of a circle with center (h, k) and radius r is:

(x − h)² + (y − k)² = r²

General Form

x² + y² + Dx + Ey + F = 0

Convert to standard form by completing the square.

Key Skills

• Write the equation given center and radius.
• Write the equation given center and a point on the circle.
• Identify center and radius from an equation.
• Convert between standard form and general form.