Let $f(x)=\frac{1}{2x-5}$.  Find the largest $x$ which is not in the domain of $g(x)=f(f(x))$.
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Let $f(x)=\frac{1}{2x-5}$.  Find the largest $x$ which is not in the domain of $g(x)=f(f(x))$.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
\frac{27}{10}
Let $f(x)=\frac{1}{2x-5}$.  Find the largest $x$ which is not in the domain of $g(x)=f(f(x))$.
train