If f(x)=3x4 − 7x2 + 2x − 9, then f(−x) =

f(x)  = 3x^4 − 7x^2 + 2x − 9       ......so.....

f(-x) = 3(-x)^4 - 7(-x)^2 + 2(-x)  - 9  =    3x^2 - 7x^2 - 2x  - 9

[  BTW.....This function is neither even nor odd....  ]