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# gcd

Greatest common divisor of polynomials

### Use only in the MuPAD Notebook Interface.

This functionality does not run in MATLAB.

## Syntax

```gcd(p, q, …)
gcd(f, g, …)
```

## Description

gcd(p, q, ...) returns the greatest common divisor of the polynomials p, q, … The coefficient ring of the polynomials may either be the integers or the rational numbers, Expr, a residue class ring IntMod(n) with a prime number n, or a domain.

All polynomials must have the same indeterminates and the same coefficient ring.

Polynomial expressions are converted to polynomials. See poly for details.

The return value is of the same type as the input polynomials, i.e., either a polynomial of type DOM_POLY or a polynomial expression.

gcd returns 0 if all arguments are 0, or if no argument is given. If at least one of the arguments is - 1 or 1, then gcd returns 1.

Use igcd if all arguments are known to be integers, since it is much faster than gcd.

## Examples

### Example 1

The greatest common divisor of two polynomial expressions can be computed as follows:

`gcd(6*x^3 + 9*x^2*y^2, 2*x + 2*x*y + 3*y^2 + 3*y^3)`

```f := (x - sqrt(2))*(x^2 + sqrt(3)*x-1):
g := (x - sqrt(2))*(x - sqrt(3)):
gcd(f, g)```

One may also choose polynomials as arguments:

```p := poly(2*x^2 - 4*x*y - 2*x + 4*y, [x, y], IntMod(17)):
q := poly(x^2*y - 2*x*y^2, [x, y], IntMod(17)):
gcd(p, q)```

`delete f, g, p, q:`

## Parameters

 p, q, … polynomials of type DOM_POLY f, g, … polynomial expressions

## Return Values

Polynomial or a polynomial expression.