Find the intervals on which the function `f(x) = (x + 1)^(3) (x -3)^(3)` is (a) increasing (b) decreasing

Explanation

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

### Step 1: Differentiate the function
We will use the product rule to differentiate \( f(x) \).

Let:
- \( u = (x + 1)^3 \)
- \( v = (x - 3)^3 \)
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