Answer:
f(x) = (x - 4)^2 + 4
Step-by-step explanation:
The "vertex form" is
y - k = a(x - h)^2
Starting with f(x)=x^2-8 x+12, "complete the square:"
f(x)=x^2-8x + 16 - 16 + 12, or
f(x) = (x - 4)^2 + 4. Thus, the vertex is (4, 4).