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The center of a circle is at (−3, 1) and its radius is 9. What is the equation of the circle?

A.) (x+3)2+(y−1)2=81
B.) (x−3)2+(y+1)2=18
C.) (x−3)2+(y+1)2=81
D.) (x+3)2+(y−1)2=18

User Ceyda
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1 Answer

3 votes

If a circle has center (a,b) and radius r, the equation is


(x-a)^2+(y-b)^2=r^2

So, you have


(x+3)^2+(y-1)^2=81

User Greg Elin
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