SOLUTION: Find the radius of a circle: x^2 + y^2 + 4x -4y- 1 = 0

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Question 450238: Find the radius of a circle:
x^2 + y^2 + 4x -4y- 1 = 0
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi

Standard Form of an Equation of a Circle is %28x-h%29%5E2+%2B+%28y-k%29%5E2+=+r%5E2

where Pt(h,k) is the center and r is the radius

x^2 + y^2 + 4x -4y- 1 = 0  |completing squares

(x+2)^2-4 +(y-2)^2-4 -1 = 0

%28x%2B2%29%5E2+%2B+%28y-2%29%5E2+=+9