Well the rational roots theorem tells you that all the rational roots are of the form a/b where a is a (positive or negative) divisor of the constant term and b a divisor of the coefficient of the term of highest degree.

Well the rational roots theorem tells you that all the rational roots are of the form a/b where a is a (positive or negative) divisor of the constant term and b a divisor of the coefficient of the term of highest degree.

In this case it means that possible values of \(\displaystyle a\) are \(\displaystyle \pm 1\), \(\displaystyle \pm 2\) and \(\displaystyle b\) are \(\displaystyle 1, 2, 4\)