
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 the sequences \( \left\{a_{n}\right\} \) and \( \left\{b_{n}\right\} \) such that
\[
\begin{array}{l}
a_{1} = -1, \quad b_{1} = 2, \\
a_{n+1} = -b_{n}, \quad b_{n+1} = 2a_{n} - 3b_{n} \quad (n \in \mathbb{Z}_{+}).
\end{array}
\]
Find the value of \( b_{2015} + b_{2016} \).

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