Question

Identify the center and radius for the circle with the following equation; (x+5)^2+y^2+12y=3

Answer 1

Center: (-5,-6)
Radius: 39
How to do it

Complete the square for
y
2
+
12
y
y
2
+
12
y
.

(
y
+
6
)
2
−
36
(
y
+
6
)
2
-
36
Substitute
(
y
+
6
)
2
−
36
(
y
+
6
)
2
-
36
for
y
2
+
12
y
y
2
+
12
y
in the equation
(
x
+
5
)
2
+
y
2
+
12
y
=
3
(
x
+
5
)
2
+
y
2
+
12
y
=
3
.
(
x
+
5
)
2
+
(
y
+
6
)
2
−
36
=
3
(
x
+
5
)
2
+
(
y
+
6
)
2
-
36
=
3
Move
−
36
-
36
to the right side of the equation by adding
36
36
to both sides.
(
x
+
5
)
2
+
(
y
+
6
)
2
=
3
+
36
(
x
+
5
)
2
+
(
y
+
6
)
2
=
3
+
36
Add
3
3
and
36
36
.
(
x
+
5
)
2
+
(
y
+
6
)
2
=
39
(
x
+
5
)
2
+
(
y
+
6
)
2
=
39
This is the form of a circle. Use this form to determine the center and radius of the circle.