f (x) =-3x4+2,5x2 доказать нечетность

                                    N1
 13-100х=0
                                      N2
 8-0,8х=0
                                      N3
  7х-4=х-16
                                     N4
 1,3р-11=0,8р+5

                                                N1
   13-5х=8-2х
                                                         N2
           4у+15=6н+17
                                                      N3

          8с+0.73=4,61-8с
                                                       N4

                  5х+(3х-7)=9
                                                              N5

         48=11-(9а+2)
                                                N6
           13-(5х+11)=6х
                                 N7
(7х+11)-(6х+3)=5
                                                 N8
             2=(3х-5)-(7-4х)
  решите пожалуйста я вас очень прошу, отблагадарю!