Question

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

Answer 1

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

Explanation:

Recall that the eqn. of a circle having centre at `(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.`