Given:
The equations of circle are
4.
5.
6 .

To find:
The center and radius for the given circles.
Solution:
The standard form of a circle is:

Where,
is center and
is the radius of the circle.
4.
The equation of the circle is

The standard form of this circle is


Therefore, the center of the circle is
and the radius of the circle is
.
5.
The equation of the circle is

The standard form of this circle is


Therefore, the center of the circle is
and the radius of the circle is
.
6.
The equation of the circle is

The standard form of this circle is


Therefore, the center of the circle is
and the radius of the circle is
.