f(x) = f(-x) is even, and f(-x)=-f(x) is odd. to know if it's even or odd you take the function and plug in -x for x then simplify it. if it's the same function that you started with , it's even. for example
if you have this
f(x) = -3x^2+4
plug in -x for x which will turn out to be
f(-x) = -3(-x)^2+4
and when simplified it'll be
-3x^2+4 because (-x)^2 is (-x)(-x) which is a positive.
because it's the same, it's an even one.
