(3х - 1)(3х + 1) – (х - 1)(х + 2) = 8

9x^2-1-(x^2+2x-x-2)=8

8x^2+1-x-8=0

8x^2-x-7=0

D=(-1)^2+4×7×8=225

x=1

x=-15/16

Объяснение:

9x^2 - 1 - x^2 + 2 +x -2x =8

8x^2 +1 -x=8

8x^2 - x= 7

8x^2 - x - 7 =0

D= 1 + 4×8×7=225=15^2

x1= 1 - 15 / 16 = - 14/16 = -7/8

x2= 1 +15/16 = 1

1 и -7/8