Q. 73.9( 62 Votes )

In each of the following, find the centre and radius of the circles.

x2 + y2 – 4x – 8y – 45 = 0

Answer :

The equation of the given circle is x2 + y2 – 4x – 8y – 45 = 0.


x2 + y2 – 4x – 8y – 45 = 0


(x2 – 4x) + (y2 -8y) =45


+ – 4 – 16 = 45


(x - 2)2 + (y – 4)2 =65


(x - 2)2 + (y – 4)2 =, which is form (x-h)2 +(y-k)2 = r2, where h=2,


K= 4 and r=


Thus, the centre of the given circle is (2, 4), while its radius is.


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