1. Substitute \( x-3 \) for \( x \) in the function \( f(x) \):
    f(x-3) = (x-3)^2 - 6(x-3) + 4 
2. Expand and simplify the squared term:
    (x-3)^2 = x^2 - 6x + 9 
3. Then distribute the -6:
    -6(x-3) = -6x + 18 
4. Substitute these into the equation:
    f(x-3) = x^2 - 6x + 9 - 6x + 18 + 4 
5. Combine like terms:
    f(x-3) = x^2 -12x + 31 
So the answer is:
    f(x-3) = x^2 - 12x + 31