Geometry and TrigonometryEasyCentre of a circle from its equation
Geometry and Trigonometry practice question
In the xy-plane, what is the centre of the circle (x − 3)² + (y + 2)² = 9?
- A. (3, −2)Correct
- B. (−3, 2)
- C. (3, 2)
- D. (−3, −2)
Answer: A. (3, −2)
The equation (x − h)² + (y − k)² = r² has centre (h, k), and y + 2 is y − (−2).
Why the other answers are wrong
- B. (−3, 2)
- Both signs are reversed.
- C. (3, 2)
- The sign of the y-coordinate is reversed.
- D. (−3, −2)
- The sign of the x-coordinate is reversed.
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