Answer:
y = (x - 6)^2 - 20
Explanation:
Let's start by completing the square for x^2 - 12x. Half of the coefficient of x is (1/2)(-12), or -6. Square this and add it to x^2 - 12x, and then subtract it:
x^2 - 12x + 36 - 36 + 23 = 7
Rewriting the first three terms,
(x - 6)^2 -13 = 7, or
y = (x - 6)^2 - 20
The vertex is located at (h,k), which here is (6, -20).