(3x-1)(3x+1)-(x-1)(x+2)=8

(3x-1)(3x+1)-(x-1)(x+2)=8

(9х²-1)-(х²+2х-х-2)=8

9х²-1-х²-х+2=8

8х²-х+1-8=0

8х²-х-7=0

Д= 1-4*8*(-7)=225

х₁= 1-15/16=-14/16= -7/8

х₂=1+15/16=1