Find the intervals in which `f(x)=2x^3-12 x^2+18 x+15` is increasing or decreasing.

Explanation

To determine the intervals in which the function \( f(x) = 2x^3 - 12x^2 + 18x + 15 \) is increasing or decreasing, we will follow these steps:

### Step 1: Find the derivative of the function
We start by finding the first derivative \( f'(x) \) of the function \( f(x) \).

\[ f'(x) = \frac{d}{dx}(2x^3 - 12x^2 + 18x + 15) \]
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