HKDSE Core Math by DreyfusGeometry: Circles Course Notes

Circles Equation of circle: (x-a) + (y-b) = rwhere (a, b) is the centre of circle, r is radius. General equation of circle: x + y + Ax + By + C = 0where centre = (-0.5A, -0.5B)and radius =

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HKDSE Core Math by DreyfusGeometry: Circles Course Notes

Example 1 What is the center of the circle (x - 5) + (y + 3) = 49?

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HKDSE Core Math by DreyfusGeometry: Circles Course Notes

Example 2

What is the center of the circle x + y + 8x - 12y + 27 = 0?

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HKDSE Core Math by DreyfusGeometry: Circles Course Notes

Example 3 What is the radius of the circle x + y - 6x + 14y - 23 = 0?

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HKDSE Core Math by DreyfusGeometry: Circles Course Notes

Example 4

What is the equation of the circle with center (2, -5) and which has the same radius as the circle x + y + 6x + 8y - 24 = 0?

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HKDSE Core Math by DreyfusGeometry: Circles Course Notes

Example 5

Which one of the following is the equation of a circle?

I. x + y + 4x - 6y + 5xy - 12 = 0II. x - y + 4x - 6y + 16 = 0III. x + y + 4x - 6y - 12 = 0IV. x + y - 4x - 6y + 16 = 0

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