What is the center of the circle and the radius
X2+y2-4x+12y-24=0

Subtract

31

31

from both sides of the equation.

x

2

+

y

2

−

4

x

−

12

y

=

−

31

x2+y2-4x-12y=-31

Complete the square for

x

2

−

4

x

x2-4x

.

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(

x

−

2

)

2

−

4

(x-2)2-4

Substitute

(

x

−

2

)

2

−

4

(x-2)2-4

for

x

2

−

4

x

x2-4x

in the equation

x

2

+

y

2

−

4

x

−

12

y

=

−

31

x2+y2-4x-12y=-31

.

(

x

−

2

)

2

−

4

+

y

2

−

12

y

=

−

31

(x-2)2-4+y2-12y=-31

Move

−

4

-4

to the right side of the equation by adding

4

4

to both sides.

(

x

−

2

)

2

+

y

2

−

12

y

=

−

31

+

4

(x-2)2+y2-12y=-31+4

Complete the square for

y

2

−

12

y

y2-12y

.

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(

y

−

6

)

2

−

36

(y-6)2-36

Substitute

(

y

−

6

)

2

−

36

(y-6)2-36

for

y

2

−

12

y

y2-12y

in the equation

x

2

+

y

2

−

4

x

−

12

y

=

−

31

x2+y2-4x-12y=-31

.

(

x

−

2

)

2

+

(

y

−

6

)

2

−

36

=

−

31

+

4

(x-2)2+(y-6)2-36=-31+4

Move

−

36

-36

to the right side of the equation by adding

36

36

to both sides.

(

x

−

2

)

2

+

(

y

−

6

)

2

=

−

31

+

4

+

36

(x-2)2+(y-6)2=-31+4+36

Simplify

−

31

+

4

+

36

-31+4+36

.

(

x

−

2

)

2

+

(

y

−

6

)

2

=

9

(x-2)2+(y-6)2=9

This is the form of a circle. Use this form to determine the center and radius of the circle.

(

x

−

h

)

2

+

(

y

−

k

)

2

=

r

2

(x-h)2+(y-k)2=r2

Match the values in this circle to those of the standard form. The variable

r

r

represents the radius of the circle,

h

h

represents the x-offset from the origin, and

k

k

represents the y-offset from origin.

r

=

3

r=3

h

=

2

h=2

k

=

6

k=6

The center of the circle is found at

(

h

,

k

)

(h,k)

.

Center:

(

2

,

6

)

(2,6)

These values represent the important values for graphing and analyzing a circle.

Center:

(

2

,

6

)

(2,6)

Radius:

3

3

center: (2,-6)

radius: 8

Step-by-step explanation:

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