Find the intervals in which `f(x)=(x+1)^3(x-1)^3` is increasing or decreasing.

Explanation

To determine the intervals where the function \( f(x) = (x+1)^3 (x-1)^3 \) is increasing or decreasing, we will follow these steps:

### Step 1: Find the derivative \( f'(x) \)

We start by differentiating the function \( f(x) \).

1. **Rewrite the function**:
\[
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