What is the radius of the circle given by the equation below?

x2 + 12x + y2 - 12y = - 56

A. 2

B. 16

C. 4

D. 8

C

Step-by-step explanation:

First, you gotta complete the square!

x^2+12x+36 = (x+6) ^2

y^2-12y+36 = (y-6) ^2

So, we have (x+12) ^2 + (y-6) ^2 = - 56 + 36 + 36

The right side of the equation is the radius^2.

Simplify:

-56 + 36 + 36 = 16

The square root of 16 is 4, so the answer is C!