The condition for a function to be even is:
[tex]f(x)=f(-x)[/tex]We substitute x by -x in our options and see of we get the same original function, if we do then it is an even function.
First function:
[tex]f(x)=x^4-x^2[/tex]And for f(-x) here we have:
[tex]f(-x)=(-x)^4-(-x)^2[/tex]Even exponents always give positive results, so:
[tex]f(-x)=x^4-x^2[/tex]This is an even function.