The rational root theorem tells you that a rational root of this is the ratio of a factor of the constant term to that of a factor of the coefficient of the highest power of the variable.

So the candidates are 2, 1, 2/3, 1/3, try them in turn, if one is a root then take out the corresponding factor leaving you with a quadratic. Now use the quadratic formula, complete the square or whatever to find the roots of this quadratic.

CB