### Home > CCG > Chapter 12 > Lesson 12.2.4 > Problem12-105

12-105.

Describe each circle by finding the center and radius. You need to “complete the square” to rewrite the equation in part (b) in graphing form.

1. $(x + 5)^2 + y^2 = 10$

Recall the standard form for a circle:
$(x − h)^2 + (y − k)^2 = r^2$
where the point $(h, k)$ is the circle's center and $r$ is the radius.

2. $x^2 − 6x + y^2 − 2y − 5 = 0$

$(x − 3)^2 + y^2 − 2y = 5 + 9$

$(x − 3)^2 + (y − 1)^2 = 5 + 9 + 1$

Center: $(3,1)$

Radius: $\sqrt{15}$