
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
Observe the following monomials about $x$ and explore their patterns: $-x^{2}$, $3x^{4}$, $-5x^{6}$, $7x^{8}$, $-9x^{10}$, $11x^{12}$, $\ldots$. According to the above pattern, the $20$th monomial is ______.

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