Solve
Take 3 as common factor from last two factor to get
9(x-1)(x-2)(x- 2/3)(x+ 1/3) = 21
The sum of constant terms of first factor and third factor is same as the sum of the constant terms of second and fourth factor.
(3x^2-5x+2)(3x^2-5x-2) = 21
let 3x^2-5x = t
(t+2)(t-2) = 21
Solve