Solve: ( x2 + x + 1 ) ( x2 + x + 2 ) = 12
Multiply out: x4 + 2x3 + 4x2 + 3x + 2 = 12
Rewrite: x4 + 2x3 + 4x2 + 3x - 10 = 0
There are two rational solutions; you can find them by trying all the factors of -10:
1, -1, 2, -2, 5, -5, 10, -10 (two of these will work)
After you have these two solutions, you can divide their factors out of the original problem.
This will give you a quadratic that can be solved by using the quadratic equation.