
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]


system
Given $a < b < 0$, which of the following inequalities does not hold? Fill in the blank with the serial number only.  
① $\frac{1}{a} > \frac{1}{b}$  
② $\frac{1}{a-b} > \frac{1}{a}$  
③ $|a| > |b|$  
④ $a^2 > b^2$

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