Daniel B. answered 12/08/21
A retired computer professional to teach math, physics
This is an application of the Rational Root Theorem.
Any irreducible rational root of a polynomial is of the form
±p/q
where p and q are relatively prime positive integers with the property:
1. p must be a divisor of the constant coefficient, which in your case is 1.
So the only possibility is p = 1.
2. q must be a divisor of the highest-order coefficient, which in your case is 3.
So you have two options for q -- q = 1 or q = 3.
In total there are only four candidates for rational coefficients of the equations:
1/1, 1/3, -1/1, -1/3
You can plug them into the equation to see if any of them is a root.