Find the intervals for which `f(x)=x^4-2x^2` is increasing or decreasing.

Explanation

To find the intervals where the function \( f(x) = x^4 - 2x^2 \) is increasing or decreasing, we will follow these steps:

### Step 1: Find the derivative of the function
To determine where the function is increasing or decreasing, we first need to find the derivative of \( f(x) \).

\[ f'(x) = \frac{d}{dx}(x^4 - 2x^2) = 4x^3 - 4x \]
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