
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 that the derivative of the function $f(x)=x^2 -2x$ is denoted as $f'(x)$, and the sequence ${a_n} = f'(n)$, find the sum of the first $n$ terms of the sequence, denoted as $S_n$.

A) ${n^2}+n$
B) ${n^2}-n$
C) ${n^2}+2n$
D) ${n^2} -2n$

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