
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
The sequence {a_n} is an arithmetic sequence, and S_n denotes the sum of its first n terms. If S_5 = 2a_5 and a_3 = -4, find a_9.

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