## College Algebra 7th Edition

We convert the equation to the circle formula by completing the square: $x^2+y^2+72=12x$ $(x^2-12x)+y^2=-72$ $(x^2-12x+36)+y^2=-72+36$ $(x-6)^2+y^2=-36$ Since $r^2$ is negative this equation does not make sense and has no graph.