SOLUTION: Find the center and radius of the circle defined by the equation: X^2+Y^2+4X-8Y+13=0 Please!! Help!

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Question 781417: Find the center and radius of the circle defined by the equation:
X^2+Y^2+4X-8Y+13=0
Please!! Help!

Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
You want the equation in a form, %28x-h%29%5E2%2B%28y-k%29%5E2=r%5E2 in which the center is (h,k) and radius is r. This is a Complete-the-Square problem.

x%5E2%2By%5E2%2B4x-8y%2B13=0
x%5E2%2B4x%2By%5E2-8y%2B13=0
The terms with x need %284%2F2%29%5E2=4 and the terms with y need %28-8%2F2%29%5E2=16

%28x%5E2%2B4x%2B4%29%2B%28y%5E2-8y%2B16%29%2B13=4%2B16

(x+2)^2+(y-4)^2=7

Center: (-2,4)
Radius: sqrt(7)