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# What is the centre and radius of a circle when x squared plus y squared -4x -2y -4 equals 0?

Equation: x^2 +y^2 -4x -2y -4 = 0

Completing the squares: (x-2)^2 +(y-1)^2 -4-1-4 = 0

So: (x-2)^2 +(y-1)^2 = 9

Therefore the centre of the circle is at (2, 1) and its radius is 3

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You need to change the equation to the form (x - a) squared + (y - b) squared = r squared. You do this by completing the square. In this case, (a, b) will be the center of the circle, and r will be the radius.

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If: x^2+y^2 -4x -2y -4 = 0 Then by completing the squares of x and y: (x-2)^2+(y-1)^2 = 9 Therefore the centre of the circle is at (2, 1) and its radius is 3 units

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