Substitute -x for x.
2(-x)7 - (-x)3 + 2
Two negative numbers multiply to a positive product, right? With odd exponents, a negative base stays negative.
(-5)5 = (-5)(-5)(-5)(-5)(-5) = -3125
So, we end up with -2x7 + x3 + 2
That's not the original function, and the last sign (+2) didn't change, so it's NEITHER.