Evaluate the circle equation:
(x - 2)
2 + (y + 5)
2 = 81
This circle equation is in standard form:
(x - h)
2 + (y - k)
2 = r
2Determine 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 r
2 = 81
r = ±√
81Since a radius is always positive
We have r =
9General form of circle equation
Center (
h,
k) = (
-2,
+5) and r =
r =
9:
Expand the standard form
x
2 + y
2 - 2
hx - 2
ky +
h2 +
k2 -
r2 = 0
Plugg in our values for h,k, and r:
x
2 + y
2 - 2(
-2)x - 2(
+5)y +
-22 +
+52 -
92 = 0
x
2 + y
2 + 4x - 10y + 4 + 25 - 81 = 0
Combine our constants
x2 + y2 + 4x - 10y - 52 = 0To see the diameter, circumference, and area of this circle, visit our
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