
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 following four statements:
1. The integral $$\int_{-a}^{a} (x^2 + \sin x) \, dx = 18$$, then $a=3$.
2. The coefficient of determination, denoted as $R^2$, is used to describe the quality of fit of the regression. The larger the value of $R^2$, the worse the fit of the model.
3. If $f(x)$ is an odd function defined on $\mathbb{R}$, and it satisfies $f(x+2) = -f(x)$, then the graph of the function $f(x)$ is symmetric about $x=1$.
4. Given that the random variable $\xi$ follows a normal distribution $N(1, \sigma^2)$, and if $P(\xi \leq 4) = 0.79$, then $P(\xi < -2) = 0.21$.
The correct statement(s) is/are ________.

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