Find all the points of local maxima and minima of the function `f(x)=x^3-6x^2+9x+15` .

Explanation

To find the points of local maxima and minima of the function \( f(x) = x^3 - 6x^2 + 9x + 15 \), we will follow these steps:

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

\[ f'(x) = \frac{d}{dx}(x^3 - 6x^2 + 9x + 15) \]
...