
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
Consider an arithmetic sequence where each term increases by 1 and the first term is \( k^2 + k \). Find the sum of the first \( 3k \) terms of this sequence.
**A)** \( 3k^3 + 7k^2 - 2k \)  
**B)** \( 3k^3 + \frac{15}{2}k^2 - \frac{3}{2}k \)  
**C)** \( 2k^3 + 5k^2 + k \)  
**D)** \( 3k^3 + 5k^2 - k \)

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