The equation x^2 + 6x + y^2 + 6y = 78 represents a circle. What is its center? Write your answer as an ordered pair.
x^2 + 6x + y^2 + 6y = 78 complete the square on x and y
x^2 + 6x + 9 + y^2 + 6y + 9 = 78 + 9 + 9
(x + 3)^2 + ( y + 3)^2 = 96
The center is ( -3 , -3)
