Geometry Name ____________________________Pd. ____7.7 Equation of a Circle

Match the equation of a circle with its description.

________ 1. x2 + y2 = 4

________ 2. x2 + y2 = 9

________ 3. (x + 1)2 + (y – 4)2 = 16

________ 4. (x + 2)2 + (y + 3)2 = 9

________ 5. (x + 3)2 + (y – 5)2 = 16

________ 6. (x – 2)2 + (y – 5)2 = 9

A. center (–1,4), radius 4

B. center (–2,–3), radius 3

C. center (0, 0), radius 2

D. center (2, 5), radius 3

E. center (–3, 5), radius 4

F. center (0, 0), radius 3

Give the center and radius of the circle.

7. x2 + y2 = 36 Center Radius

8. (x + 4)2 + (y – 2)2 = 49 Center Radius

Write the standard equation of the circle with the given center and radius. ( x−h )2+( y−k )2=r2

9. Center (0, 3), radius 5

10. Center (7, –6), radius 9

Identify the center and radius of the circle. Then write the standard equation of the circle. ( x−h )2+( y−k )2=r2

11. _____________________________________ 12. _____________________________________

Center _________ Center _________

Radius _________ Radius _________

13. _____________________________________ 14. _____________________________________

Center _________ Center _________

Radius _________ Radius _________

Identify the center and radius of the circle. Then sketch the graph.

15. x2 + y2 = 25 16. (x – 1)2 + y2 = 16

Center _________ Center _________

Radius _________ Radius _________

17. x2 + (y + 2)2 = 9 18. (x + 3)2 + (y – 1)2 = 4

Center _________ Center _________

Radius _________ Radius _________

Review: Find the value of x. Show work!

19. x = _________ 20. x = _________ 21. x = _________

22. x = _________ 23. x = _________ 24. x = _________