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Write the equation of a circle from its centre and radius

10th grade (Year 11 in England) · 16 questions · Common Core: HSG.GPE.A.1 · England: GCSE Higher Algebra

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  1. Question 1

    Where is the point (9, −1) relative to the circle (x − 5)² + (y + 4)² = 36?

    • A. Inside the circle
    • B. On the circle
    • C. Outside the circle
  2. Question 2

    Which is the equation of the circle with centre (−5, −1) and radius 3?

    • A. (x − 5)² + (y − 1)² = 9
    • B. (x + 5)² + (y + 1)² = 3
    • C. (x + 5)² + (y + 1)² = 9
    • D. (x − 5)² + (y − 1)² = 3
  3. Question 3

    A circle has centre (−1, 3) and passes through (5, −5). Its equation is (x + 1)² + (y − 3)² = k. Find k.

    Answer

  4. Question 4

    Where is the point (2, −1) relative to the circle (x − 2)² + (y + 1)² = 4?

    • A. Inside the circle
    • B. On the circle
    • C. Outside the circle
  5. Question 5

    Which is the equation of the circle with centre (5, 2) and radius 8?

    • A. (x + 5)² + (y + 2)² = 8
    • B. (x − 5)² + (y − 2)² = 64
    • C. (x − 5)² + (y − 2)² = 8
    • D. (x − 2)² + (y − 5)² = 64
  6. Question 6

    A circle has centre (−3, −5) and passes through (0, −4). Its equation is (x + 3)² + (y + 5)² = k. Find k.

    Answer

  7. Question 7

    Where is the point (2, −2) relative to the circle (x − 3)² + (y + 2)² = 4?

    • A. Inside the circle
    • B. On the circle
    • C. Outside the circle
  8. Question 8

    Which is the equation of the circle with centre (−1, 1) and radius 4?

    • A. (x + 1)² + (y − 1)² = 4
    • B. (x − 1)² + (y + 1)² = 4
    • C. (x + 1)² + (y − 1)² = 16
    • D. (x − 1)² + (y + 1)² = 16
  9. Question 9

    A circle has centre (−1, 0) and passes through (−1, 3). Its equation is (x + 1)² + y² = k. Find k.

    Answer

  10. Question 10

    Where is the point (13, −2) relative to the circle (x − 5)² + (y + 2)² = 64?

    • A. Inside the circle
    • B. On the circle
    • C. Outside the circle
  11. Question 11

    Which is the equation of the circle with centre (−1, 6) and radius 3?

    • A. (x − 1)² + (y + 6)² = 3
    • B. (x − 1)² + (y + 6)² = 9
    • C. (x + 1)² + (y − 6)² = 9
    • D. (x − 6)² + (y + 1)² = 9
  12. Question 12

    A circle has centre (−1, −3) and passes through (−1, 5). Its equation is (x + 1)² + (y + 3)² = k. Find k.

    Answer

  13. Question 13

    Where is the point (8, 2) relative to the circle (x + 1)² + (y − 1)² = 64?

    • A. Inside the circle
    • B. On the circle
    • C. Outside the circle
  14. Question 14

    Which is the equation of the circle with centre (3, −6) and radius 7?

    • A. (x − 3)² + (y + 6)² = 7
    • B. (x + 6)² + (y − 3)² = 49
    • C. (x − 3)² + (y + 6)² = 49
    • D. (x + 3)² + (y − 6)² = 7
  15. Question 15

    A circle has centre (3, 3) and passes through (1, 0). Its equation is (x − 3)² + (y − 3)² = k. Find k.

    Answer

  16. Question 16

    Where is the point (−3, 3) relative to the circle (x + 3)² + (y − 4)² = 16?

    • A. Inside the circle
    • B. On the circle
    • C. Outside the circle

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Answer key: Write the equation of a circle from its centre and radius

  1. 1. A. Inside the circle

  2. 2. C. (x + 5)² + (y + 1)² = 9

  3. 3. 100

  4. 4. A. Inside the circle

  5. 5. B. (x − 5)² + (y − 2)² = 64

  6. 6. 10

  7. 7. A. Inside the circle

  8. 8. C. (x + 1)² + (y − 1)² = 16

  9. 9. 9

  10. 10. B. On the circle

  11. 11. C. (x + 1)² + (y − 6)² = 9

  12. 12. 64

  13. 13. C. Outside the circle

  14. 14. C. (x − 3)² + (y + 6)² = 49

  15. 15. 13

  16. 16. A. Inside the circle