
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 $f(x)$ is an even function defined on the real number line $\mathbb{R}$, and $f(x)$ is an increasing function on the interval $[0, +\infty)$, if for any $x \in [1,2]$, the inequality $f(ax+1) \leqslant f(x-3)$ is always true, then the range of values for the real number $a$ is _______.

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