
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
If $z=1+i$, and $(x+z)^4=a_0x^4+a_1x^3+a_2x^2+a_3x+a_4$ ($a_i\in\mathbb{C}$, $i=0,1,2,3,4$), then $a_2=$ \_\_\_\_\_\_.

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