SOLUTION: the circle with equation 2(x+4)^2+2(y-1)^2-18=0 has centre C and radius r units, where..?

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Question 1158137: the circle with equation 2(x+4)^2+2(y-1)^2-18=0 has centre C and radius r units, where..?
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
Learn that

%28x-h%29%5E2%2B%28y-k%29%5E2=r%5E2

is the equation of a circle with center (h,k) and radius r units.  

Your equation is 

2%28x%2B4%29%5E2%2B2%28y-1%29%5E2-18=0

Make it look like this:

      %28x-h%29%5E2%2B%28y-k%29%5E2=r%5E2

Divide every term by 2

2%28x%2B4%29%5E2%2F2%2B2%28y-1%29%5E2%2F2-18%2F2=0%2F2

%28x%2B4%29%5E2%2B%28y-1%29%5E2-9=0

Add +9 to both sides:

%28x%2B4%29%5E2%2B%28y-1%29%5E2=9

Now it looks like 

%28x-h%29%5E2%2B%28y-k%29%5E2=r%5E2

-h = +4;   -k = -1
 h = -4;    k =  1
 r² = 9
  r = 3

Therefore the center is (-4,1) and the radius in 3, and the
graph looks like this:



Edwin