What real values of $x$ are not in the domain of

$f(x)=\frac{1}{|x^2-6x+8|+|x^2+x-6|}$?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
What real values of $x$ are not in the domain of

$f(x)=\frac{1}{|x^2-6x+8|+|x^2+x-6|}$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
2
What real values of $x$ are not in the domain of

$f(x)=\frac{1}{|x^2-6x+8|+|x^2+x-6|}$?
train