Question

How do you identify the center and the radius of a circle with the equation `(x + 5)^2 + (y + 3)^2 = 49`?

Answer 1

centre = ( - 5 , - 3 ) and radius = 7

Explanation:

The standard form of the equation of a circle is:

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

where (a , b ) are the coordinates of the centre and r is radius.

compare `(x + 5 )^2 + (y + 3 )^2 =49` with standard form

a = -5 and b = - 3 hence centre = ( - 5 , - 3 )

and `r^2 = 49 rArr r = sqrt49 = 7`