Radius and Center (h,k)=(,) and r =
Diameter Points A = (,) B = (,)
Circle Equation

  

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Evaluate the circle equation:
(x - 2)² + (y + 5)² = 81

This circle equation is in standard form:
(x - h)² + (y - k)² = r²

Determine h:

h = -1 * -2 = 2

Determine k:

k = -1 * +5 = -5

Determine center of the circle:

Therefore, our circle has a center (h, k) = (2, -5)

Determine radius:

Therefore, we have r² = 81
r = ±√81
Since a radius is always positive
We have r = 9

General form of circle equation

Center (h, k) = (-2, +5) and r = r = 9:

Expand the standard form

x² + y² - 2hx - 2ky + h² + k² - r² = 0

Plugg in our values for h,k, and r:

x² + y² - 2(-2)x - 2(+5)y + -2² + +5² - 9² = 0
x² + y² + 4x - 10y + 4 + 25 - 81 = 0

Combine our constants

x² + y² + 4x - 10y - 52 = 0

To see the diameter, circumference, and area of this circle, visit our calculator