## Precalculus (10th Edition)

We know that if a function is odd, then $f(-x)=-f(x).$ We know that if a function is even, then $f(-x)=f(x).$ Hence, we plug in $-x$ into $x$ to see what happens. $f(-x)=2(-x)^4-(-x)^2\\ f(-x)=2\cdot(x^4)-x^2\\ f(-x)=2x^4-x^2\\ f(-x)=f(x)$ Therefore the function is even.