Hi,
Showing graphically:
x^2+y^2+2x+2y=0 |completing squares
x^2+2x+ y^2+2y =0
(x+1)^2 -1 + (y+1)^2 -1 = 0
(x+1)^2 + (y+1)^2 = 2
x^2+y^2+4x+6y+12=0 |completing squares
x^2+4x + y^2+6y +12=0
(x+2)^2 -4 + (y+3)^2 -9 + 12 = 0
(x+2)^2 + (y+3)^2 -9 = 1
Algebraically:
x^2+y^2+2x+2y = x^2+y^2+4x+6y+12
-12 = 2x + 4y
-x/2 - 3 = y
x^2 + (-x/2 -3)^2 + 2x + 2(-x/2-3) = 0
x^2 + x^2/4 +3x +9 +2x -x - 6 = 0
4x^2 + x^2 + 12x + 36 + 8x - 4x - 24 = 0
5x^2 +16x + 12 = 0
x = -2 x = -1.2
-x/2 - 3 = y | x = -2, y = -2 |x = -1.2, y = -2.4
Solution: Pt(-2,-2) and Pt(-1.2,-2.4)