Which of the following functions are even and which odd? `f(x)=x^4+x^2`

Explanation

To determine whether the function \( f(x) = x^4 + x^2 \) is even, odd, or neither, we will follow these steps:

### Step 1: Understand the definitions of even and odd functions
- A function \( f(x) \) is **even** if \( f(-x) = f(x) \) for all \( x \).
- A function \( f(x) \) is **odd** if \( f(-x) = -f(x) \) for all \( x \).

### Step 2: Calculate \( f(-x) \)
We need to find \( f(-x) \):
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