This page presents a calculator, solving problem of finding real roots of polynomials. That means, the calculator is solving the following equation

an x n + an-1 x n-1 . . . + a1 x + a0 = 0

Roots of low order polynomials can be expressed in form of more or less complicated formula. But there is no formula for polynomials of degree 5 or higher (n ≥ 5). In such cases, different algorithms are to be employed in to find approximation or roots.

## What you should know about polynomials

(but you don't have to, if you use the calculator)

### Fundamental theorem of algebra

The fundamental theorem of algebra states, that polynomial has n real or complex roots, counting multiplicities.

### Descartes' rule of signs

If the terms of a single-variable polynomial with real coefficients are ordered by descending variable exponent, then the number of positive roots of the polynomial is either equal to the number of sign differences between consecutive nonzero coefficients, or is less than it by an even number. Multiple roots of the same value are counted separately.