Find Center and Radius of Circle

In summary, the center of the circle is at (5, -1) and the radius is 4. This can be found by completing the square for both the x and y terms in the equation.
  • #1
mathdad
1,283
1
Determine the center and the radius of circle.

x^2 + y^2 - 10x + 2y + 17 = 0

Can this be done using completing the square?
 
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  • #2
RTCNTC said:
Determine the center and the radius of circle.

x^2 + y^2 - 10x + 2y + 17 = 0

Can this be done using completing the square?
Yes! Write the equation in the form $(x^2 - 10x +\ ?) + (y^2 + 2y +\ ?) =\ ?$ (choosing the queries so as to complete the squares), and you should be able to read off the answer.
 
  • #3
Opalg said:
Yes! Write the equation in the form $(x^2 - 10x +\ ?) + (y^2 + 2y +\ ?) =\ ?$ (choosing the queries so as to complete the squares), and you should be able to read off the answer.

I got it.
 

1. What is the formula for finding the center and radius of a circle?

The formula for finding the center and radius of a circle is (h,k) for the center and r for the radius, where h and k are the coordinates of the center and r is the distance from the center to any point on the circle. The formula can also be written as (x-h)^2 + (y-k)^2 = r^2.

2. How can I find the center and radius of a circle from an equation?

To find the center and radius of a circle from an equation, first rearrange the equation into the standard form (x-h)^2 + (y-k)^2 = r^2. The values of h and k will be the coordinates of the center, and the square root of r^2 will give you the radius.

3. Can I find the center and radius of a circle using only two points on the circle?

Yes, you can find the center and radius of a circle using only two points on the circle. First, find the midpoint of the line segment connecting the two points. This will be the center. Then, find the distance between one of the points and the center using the distance formula. This distance will be the radius.

4. What information do I need to find the center and radius of a circle?

To find the center and radius of a circle, you will need the coordinates of the center and the distance from the center to any point on the circle. This information can be obtained from an equation, two points on the circle, or a graph.

5. Is it possible to have a negative radius for a circle?

No, it is not possible to have a negative radius for a circle. The radius represents the distance from the center to any point on the circle, so it cannot be negative. However, the center of the circle can have negative coordinates.

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