Calculadora de Zeros Racionais
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
raízes racionais de P(x) são ± (divisores de c) / (divisores de a)
About this calculator
The Rational Zeros Calculator applies the Rational Root Theorem to find all possible rational roots of a polynomial with integer coefficients. Given a polynomial P(x) = a·xⁿ + … + c, where a is the leading coefficient and c is the constant term, it computes the divisors of c and a, then generates all combinations ± (divisor of c)/(divisor of a). The result is a list of candidate rational roots, which can be tested in the polynomial to verify if they are actual roots.
The operation is simple: the user enters the coefficients of the polynomial, from the highest degree term to the constant term. The tool automatically identifies the leading coefficient (a) and constant term (c), calculates their integer divisors (positive and negative), and combines them as fractions. For example, for P(x) = 2x³ - x² - 4x + 2, divisors of c=2 are ±1, ±2 and divisors of a=2 are ±1, ±2. Possible rational roots are ±1, ±2, ±1/2.
This calculator is useful for students and professionals who need to factor polynomials or solve polynomial equations. It speeds up the process of finding rational roots, which is the first step for complete factorization. Use it in algebra, calculus, or engineering problems involving polynomials. Remember that the theorem only guarantees rational roots; irrational or complex roots are not listed.
Important precautions: the polynomial must have integer coefficients. If there are fractional coefficients, multiply the entire polynomial by the least common multiple of the denominators. Also, the generated list contains only candidates; not all will be actual roots of the polynomial. Each candidate must be tested (for example, using the Remainder Theorem) to confirm. The calculator also does not handle repeated roots; if a root has multiplicity greater than 1, it will appear only once in the list.
Frequently asked questions
What if the polynomial has fractional coefficients?
Multiply the entire polynomial by the least common multiple of the denominators to obtain integer coefficients. Then use the calculator normally.
Are all listed candidates actual roots of the polynomial?
No. The list contains only possible rational roots. You need to test each candidate in the polynomial to see if it actually yields zero.
Does the calculator find irrational or complex roots?
No. The Rational Root Theorem only generates rational candidates. Irrational roots (like √2) or complex roots are not listed.
How do I test if a candidate is a root?
Substitute the value into the polynomial. If the result is zero, it is a root. You can use synthetic division or the Remainder Theorem.
Can I use the calculator for polynomials of any degree?
Yes, as long as the coefficients are integers. The theorem works for any degree, but very high-degree polynomials may generate many combinations.