### Instruction: If $f(x) = x^4 + x^2 + 5x$, evaluate $f(5) - f(-5)$.### Response: To evaluate $f(5) - f(-5)$, I need to first find $f(5)$ and $f(-5)$ separately, and then subtract them.
To find $f(5)$, I just plug in $x = 5$ into the expression for $f(x)$ and simplify.
So, $f(5) = 5^4 + 5^2 + 5 \cdot 5 = 625 + 25 + 25 = 675$.
Similarly, to find $f(-5)$, I plug in $x = -5$ and simplify.
So, $f(-5) = (-5)^4 + (-5)^2 + 5 \cdot (-5) = 625 + 25 - 25 = 625$.
Now that I have both $f(5)$ and $f(-5)$, I can subtract them to get the final answer.
So, $f(5) - f(-5) = 675 - 625 = 50$.