Rational Roots Test
Rational Root Theorem: "The theorem that, if a rational number p/q, where p and q have no common factors, is a root of a polynomial equation with integral coefficients, then the coefficient of the term of highest order is divisible by q and the coefficient of the term of lowest order is divisible by p" ("Rational root theorem," 2012).

The rational roots test is to narrow down the possibilities for rational roots of an equation. If the remainder is zero as you divide the factor of these numbers out of the equation, then you know that you have found a factor and root as an answer. Keep in mind that this only works if the equation has rational roots, if they are irrational then they will not show up in this test.

For more information about the rational roots test click here.