
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


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Given real numbers $a$ and $b$ satisfying the equation $\frac{1}{a} = \frac{1}{b}$, then among the following five relationships:  
① $0 < b < a$; ② $a < b < 0$; ③ $0 < a < b$; ④ $b < a < 0$; ⑤ $a = b$.  
The impossible relationship(s) is/are ______________.

Present the answer in LaTex format: \boxed{Your answer}
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