
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 function $f(x)=4\cos (3x+φ)(|φ| < \dfrac{π}{2})$, its graph is symmetric about the line $x=\dfrac{11π}{12}$. When $x\_1$, $x\_2∈(−\dfrac{7π}{12},−\dfrac{π}{12})$, $x\_1≠x\_2$, and $f(x\_1)=f(x\_2)$, determine the value of $f(x\_1+x\_2)$.

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