Answer :
y² + 12x - 6y + 21 = 0
- 21 - 21
y² + 12x - 6y = -21
12x + y² - 6y = -21
12x + (y² - 6y + 9) = -21 + 9
12x + (y - 3)² = -12
-12 -12 -12
-x + (y - 3)² = 1
-12
- 21 - 21
y² + 12x - 6y = -21
12x + y² - 6y = -21
12x + (y² - 6y + 9) = -21 + 9
12x + (y - 3)² = -12
-12 -12 -12
-x + (y - 3)² = 1
-12