А) (6х-2у)(5х+3у) - 8ху = 30х²-18ху-10ху-6у² - 8ху = 30х²-6у²
б) (х-2)(х+3) - 4х(х+1) = х²+3х-2х-6- 4х² -4х = -3х²-3х-6
в) 2с(1+с) -(с-2)(с+4) = 2с+2с² - (c²+4c-2c-8)=2c+2c²-c²-4c+2c+8=c²+8
г) -2а(2а-3) -(2а+3)(3-2а) = -4а²+6а -(6а-4а²+6-6а) = -4а²+6а -6а+4а²-6+6а= 6а-6