Find the intervals in which the function `f(x)=2x^3+9x^2+12 x+20` is (i) increasing (ii) decreasing

Explanation

To find the intervals in which the function \( f(x) = 2x^3 + 9x^2 + 12x + 20 \) is increasing or decreasing, we will follow these steps:

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

\[ f'(x) = \frac{d}{dx}(2x^3 + 9x^2 + 12x + 20) \]
...