SOLUTION: The equation x^2+y^2-2x-4y-4=0 represents a circle. What are the coordinates for the center of the circle? What is the length of the radius of the circle?

Question 1026719: The equation x^2+y^2-2x-4y-4=0 represents a circle. What are the coordinates for the center of the circle? What is the length of the radius of the circle?
Answer by mathmate(429) (Show Source): You can put this solution on YOUR website!

Question:
The equation x^2+y^2-2x-4y-4=0 represents a circle. What are the coordinates for the center of the circle? What is the length of the radius of the circle?

Solution:
The general equation of a circle centred at (a,b) with radius r is written as:
........ (1)
By completing squares, we have

=
=
=
=0
Hence the equation of the circle can be rewritten as
(x-1)^2+(y-2)^2=3^3
By comparison with the general equation (1) above, we conclude that the centre of the circle is (a,b)=(1,2) and the radius is 3.

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