Precalculus Advanced

Polynomial Zeros Finder

Find all real and complex zeros of a polynomial up to degree 5. Enter coefficients, then see every step: rational root candidates, synthetic division tables, quadratic formula for irreducible quadratics, and a graph with all real zeros marked.

Live Calculator · Step-by-Step · Precalculus
Rational Root Theorem
Synthetic Division
Complex Roots
Degrees 2 – 5
Polynomial Zeros Finder — Degree 2–5
Select degree
Enter coefficients (integers)
All coefficients must be integers. Leading coefficient must be non-zero.
Examples
All Zeros
Enter integer coefficients above, choose a degree, and press Find All Zeros to see every real and complex zero with full step-by-step work.
Factored Form
Step-by-Step Solution
Polynomial Graph
Rational Root Theorem
If p(x) = aₙxⁿ + … + a₀ (integer coefficients), every rational zero has form ±p/q where p | a₀ (factor of constant term) q | aₙ (factor of leading coefficient)

This theorem drastically limits the candidates to test. Once you list ±(factors of a₀)÷(factors of aₙ), you check each by evaluating p(candidate) — if it equals 0, you have a zero.

After finding a zero r, perform synthetic division by (x − r) to get a reduced polynomial of degree n − 1. Repeat until you reach a quadratic.

For the quadratic remainder ax² + bx + c, apply the quadratic formula. If the discriminant Δ = b² − 4ac is negative, the two remaining zeros are complex conjugates a ± bi.
Fundamental Theorem of Algebra
deg(p) = n ⟹ exactly n zeros in ℂ (counting multiplicity)

Every polynomial of degree n has exactly n zeros when you count over the complex numbers ℂ and include repeated roots with multiplicity. This guarantees you will always find the right number of zeros.

  • Complex zeros always come in conjugate pairs for real-coefficient polynomials.
  • A degree 5 polynomial has 1, 3, or 5 real zeros (the rest are complex pairs).
  • A repeated zero r of multiplicity k means (x − r)ᵏ divides p(x) exactly.
  • At a zero of odd multiplicity, the graph crosses the x-axis.
  • At a zero of even multiplicity, the graph touches but does not cross.

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