Then we need to solve
The rational root theorem says that if there is a rational root for this polynomial equation it is of the form .
Trial and error shows that y = -1/2 is indeed a solution. This means we can draw out a factor of the form 2y + 1:
by any method of polynomial division you choose.
So finishing the solution I get that
So we need to solve for the three solutions:
The last two are impossible, as . So we only have