We can one theorem to help us find rational roots of this polynomial.
2x^3 + x^2 - 4x - 2
We'll use Descartes' rule of signs.
Because there is 1 sign change, 1 of the 3 roots will be positive.
Now we can make the value of x -1 to see how many negative roots there will be.
-2 + 1 + 4 - 2
There are 2 sign changes, so we know there will be 2 negative roots.
Because of this, we should have 3 real, rational roots.