So here is the equation

$\displaystyle f(x) = 3x^3 - x^2 + 6x - 2$

$\displaystyle f(p/q) = ...$

After plugging in p/q and doing some basic algebra, we would get:

$\displaystyle q(-p^2 + 6pq - 2q^2) = -3p^3$

Now the book says the possible rational roots are ±1/3, ±2/3, ±1, ±2

I'm stuck on how to arrive the possible rational roots.