Solution:
Given:

The domain is the set of all possible x-values (inputs) that will make the function (output) to be real and defined.
To get the domain of the function given, we need to get the undefined or singularity points.
![\begin{gathered} f(x)\text{ will be defined only when the denominator is equal to 0.} \\ \text{Hence, singularity or undefined points will occur when,} \\ x^2-6x+8=0 \\ \text{Solving to get these points,} \\ x^2-4x-2x+8=0 \\ x(x-4)-2(x-4)=0 \\ (x-2)(x-4)=0 \\ x-2=0 \\ x=0+2 \\ x=2 \\ \\ OR \\ x-4=0 \\ x=0+4 \\ x=4 \\ \\ \text{Hence, singularity occurs at;} \\ x=2,x=4 \end{gathered}]()
The domain of the function will exist when;

Hence, the solution to the domain is;

In interval notation, the domain is;

Therefore, the final answer is;
All real numbers except 2 and 4.