Find the centre and radius of each of the following circles:

(x + 5)2 + (y + 1)2 = 9

Given that we need to find the centre and radius of the given circle (x + 5)2 + (y + 1)2 = 9.



We know that the standard equation of a circle with centre (a, b) and having radius ‘r’ is given by:


(x - a)2 + (y - b)2 = r2 - - - - - (1)


Let us convert given circle’s equation into the standard form.


(x + 5)2 + (y + 1)2 = 9


(x - ( - 5))2 + (y - ( - 1))2 = 32 - - - - (2)


Comparing (2) with (1), we get


Centre = ( - 5, - 1) and radius = 3


The centre and radius of the circle is ( - 5, - 1) and 3.


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