How do you find the center and radius of the circle given ${(x + 3)}^{2} + {(y + 7)}^{2} = 81$ $(x+3)^2+(y+7)^2=81$ ?

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Answer 1 · 2016-10-05T16:46:48

$The centre : (-3,-7) and radius r = 9 .$ $"The centre : (-3,-7) and radius "r=9.$

Recall that the eqn. of a circle having centre at $(h, k) & radius r$ $(h,k)" & radius "r$ is :

$(x-h)^2+(y-k)^2=r^2...................(star)$ .

Comparing the given eqn. with $(star)$ , we immediately find that

the centre is $(-3,-7)$ and radus $r=9.$

How do you find the center and radius of the circle given (x+3)^2+(y+7)^2=81(x+3)2+(y+7)2=81(x+3)^2+(y+7)^2=81?