Geometry and TrigonometryMediumCentre from the equation of a circle
Geometry and Trigonometry practice question
In the xy-plane, a circle has the equation (x − 5)² + (y + 1)² = 9. What is the x-coordinate of the rightmost point on the circle?
Answer: 8
The centre is (5, −1) and the radius is 3, so the rightmost point is at x = 5 + 3 = 8.
Common wrong answers
- If you answered 2
- 2 is the leftmost point.
- If you answered 5
- 5 is the centre's x-coordinate.
- If you answered 14
- 14 adds 9 instead of the radius 3.
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