SOLUTION: Find the center of a circle with the equation x2 + y2 + 2x + 4y - 9 = 0

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Question 153708: Find the center of a circle with the equation x2 + y2 + 2x + 4y - 9 = 0
Answer by orca(409) About Me  (Show Source):
You can put this solution on YOUR website!
Note that the equation of a circle in standard form is
%28x-a%29%5E2%2B%28y-b%29%5E2=r%5E2
where (a,b) is the center of the circle, r is the radius.
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First write the equation in standard form. Steps are as follows.
x2+%2B+y2+%2B+2x+%2B+4y+-+9+=+0
x%5E2%2B2x%2By%5E2%2B4y-9=0
x%5E2%2B2x%2B1-1%2By%5E2%2B4y%2B4-4-9=0
%28x%5E2%2B2x%2B1%29%2B%28y%5E2%2B4y%2B4%29-9-1-4=0
%28x%2B1%29%5E2%2B%28y%2B2%29%5E2-14=0
%28x%2B1%29%5E2%2B%28y%2B2%29%5E2=14
So the center is (-1,-2).