
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
In the sequence $\{a\_n\}$, $a\_n > 0$, and the sum of its first $n$ terms, $S\_n$, satisfies $S\_n^2 - (n^2 + 2n - 1)S\_n - (n^2 + 2n) = 0$.
(I) Find the general term formula $a\_n$ of the sequence;
(II) If $b\_n = \frac{a\_n - 5}{2^n}$, find the sum $b\_2 + b\_4 + ... + b\_{2n}$.

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