
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 $f(x)=\ln (x+ \sqrt {1+x^{2}})+ \frac {3e^{x}+1}{e^{x}+1}$ on the interval $[-k,k]$ $(k > 0)$, where $M$ is the maximum value and $m$ is the minimum value, find the value of $M+m$.

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