При x= -0,5.
(2x-7)*(49+14x+4x^2)+343-4*(2x-1)*(2x+1)

(2х-7)(49+14х+4х²)+343-4(2х-1)(2х+1)=98х-28х²+8х³-343-98х-28х²+343-4(4х²-1)=8х³-16х²+8если х=-0,5, то8(-0,5)³-16(-0,5)+8=-1-4+8=3