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

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Question 1089921: Find the radius of the circle given by the equation
x^2 +y^2 +4x+4y-1=0
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

x%5E2+%2By%5E2+%2B4x%2B4y-1=0
to find the radius of the circle, write your equation in form:
%28x-h%29%5E2%2B%28y-k%29%5E2=r%5E2 where h and k are coordinates of the center, and r is the radius
%28x%5E2+%2B4x%29%2B%28y%5E2%2B4y%29-1=0...complete squares
%28x%5E2+%2B4x%2Bb%5E2%29-b%5E2%2B%28y%5E2%2B4y%2Bb%5E2%29-b%5E2-1=0...for x part a=1 and 2ab=4=>2%2A1b=4=>b=2
for y part a=1 and 2ab=4=>2%2A1b=4=>b=2
%28x%5E2+%2B4x%2B2%5E2%29-2%5E2%2B%28y%5E2%2B4y%2B2%5E2%29-2%5E2-1=0
%28x%2B2%29%5E2-4%2B%28y%2B2%29%5E2-4-1=0
%28x%2B2%29%5E2%2B%28y%2B2%29%5E2-9=0
%28x%2B2%29%5E2%2B%28y%2B2%29%5E2=9
%28x%2B2%29%5E2%2B%28y%2B2%29%5E2=3%5E2=>the radius of the circle is r=3