Final answer:
The standard form of the equation y²−6y−12x−39=0 is (y − 3)² = 12(x − 4) after completing the square, which corresponds to option A.
Step-by-step explanation:
To express the equation y²−6y−12x−39=0 in standard form, we need to complete the square for the variable y. First, we rearrange the equation:
y² − 6y = 12x + 39
Then we add (6/2)² = 9 to both sides to complete the square:
y² − 6y + 9 = 12x + 39 + 9
Simplify and write the left side as a square:
(y − 3)² = 12x + 48
Finally, we complete the square for x by isolating x to find the standard form:
(y − 3)² = 12(x − 4)
The correct answer in standard form is (y − 3)² = 12(x − 4), which corresponds to option A.