(5с-4)³+(5с-2)³-250с³= 125с³-3*25с²*4+3*5с*16-64+125с³-3*25с²*2+3*5с*4-8-250с³= -300с²+240с-64-150с²+60с-8=
=-450с²+300с-72, при с=0,5
-450с²+300с-72= -450*0,5²+300*0,5-72=-112,5+150-72=-184,5+150=-34,5
