If the point $(2,9)$ is on the graph of $y=f(x)$, then there is one point which must be on the graph of $y=f(-x)$. What is the sum of that point's coordinates?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
If the point $(2,9)$ is on the graph of $y=f(x)$, then there is one point which must be on the graph of $y=f(-x)$. What is the sum of that point's coordinates?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
7
If the point $(2,9)$ is on the graph of $y=f(x)$, then there is one point which must be on the graph of $y=f(-x)$. What is the sum of that point's coordinates?
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