Paul's Online Notes
Home / Algebra / Graphing and Functions / Circles
Show General Notice Show Mobile Notice Show All Notes Hide All Notes
General Notice

This is a little bit in advance, but I wanted to let everyone know that my servers will be undergoing some maintenance on May 17 and May 18 during 8:00 AM CST until 2:00 PM CST. Hopefully the only inconvenience will be the occasional “lost/broken” connection that should be fixed by simply reloading the page. Outside of that the maintenance should (fingers crossed) be pretty much “invisible” to everyone.

Paul
May 6, 2021

Mobile Notice
You appear to be on a device with a "narrow" screen width (i.e. you are probably on a mobile phone). Due to the nature of the mathematics on this site it is best views in landscape mode. If your device is not in landscape mode many of the equations will run off the side of your device (should be able to scroll to see them) and some of the menu items will be cut off due to the narrow screen width.

### Section 3-3 : Circles

1. Write the equation of the circle with radius 3 and center $$\left( {6,0} \right)$$. Solution
2. Write the equation of the circle with radius $$\sqrt 7$$ and center $$\left( { - 1, - 9} \right)$$. Solution

For problems 3 – 5 determine the radius and center of the circle and sketch the graph of the circle.

1. $${\left( {x - 9} \right)^2} + {\left( {y + 4} \right)^2} = 25$$ Solution
2. $${x^2} + {\left( {y - 5} \right)^2} = 4$$ Solution
3. $${\left( {x + 1} \right)^2} + {\left( {y + 3} \right)^2} = 6$$ Solution

For problems 6 – 8 determine the radius and center of the circle. If the equation is not the equation of a circle clearly explain why not.

1. $${x^2} + {y^2} + 14x - 8y + 56 = 0$$ Solution
2. $$9{x^2} + 9{y^2} - 6x - 36y - 107 = 0$$ Solution
3. $${x^2} + {y^2} + 8x + 20 = 0$$ Solution