2
2
(
x
−
a
)
2
+
(
y
−
b
)
2
=
r
2
2
2 where (
a
,
b
) are the coordinates of the center and r is the radius to find the center we require the midpoint of the 2 given points center =
[
1
2
(
−
4+
8
)
,
1
2
(
7
−
9
)
] center
=
(
2
,
−
1
) the radius is the distance from the center to either of the 2 given points calculate the radius using the distance formula
∙ d
=
√
(
x2
−
x
1
)
2
+
(
y
2
−
y
1
)
2 let (
x
1
,
y
1)
=
(
2
,
-1
) and (
x
2
,
y
2
)
=
(
−
4
,
7
)
r
=
√
=
√
(
−
4
−
2
)
2
+
(
7
+
1
)
2
=
√
36
+
64
=
10
⇒
(
x
−
2
)
2
+
(
y
−
(
−
1
)
)
2
=
10
2
⇒
(
x
−
2
)2
+
(
y
+
1
)
2
=
100
← equation of circle
