# Centre and Radius of a circle

**Question**

From the of the circles equations, determine the radius and also the centre.

- 32 = x
^{2}+ y^{2} - -30 = x
^{2}+ y^{2}– 6x – 10y

**Answer**

- Radius = 3, Centre = (0,0)
- Radius = 2, Centre = (3,5)

*Note:*

The equation of a circle

(x-h)^{2} + (y-b)^{2} = r^{2}

Where

Center = (h,b)

Radius = r

General form of circle equation

ax^{2} + by^{2} + cx + dy + e = 0

From General form of circle equation to The equation of a circle:

Perform completing the square on the two variables in the equation.

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