Geometry

A.

x^2  + y^2 - 4x -6y -12  = 0 

x^2  - 4x   + y^2   - 6y    = 12              complete the square on x and y

x^2  - 4x  + 4  + y^2  - 6y  + 9  =  12 + 4  + 9        factor the left side

(x -  2)^2  +  ( y - 3)^2   =  25

B.  This is a circle  centered at   ( 2, 3)   with a radius of 5

C. Here's the graph :  https://www.desmos.com/calculator/e4mzndmixp