gcd takes as arguments two polynomials with
coefficients in ℤ/pℤ (p must be prime).

gcd returns the GCD of these polynomials
computed in ℤ/pℤ[x] (see also
5.28.7 for polynomials with non modular coefficients).

Input :

gcd((2*x

`^`

2+5)%13,(5*x`^`

2+2*x-3)%13)Output :

(-4%13)*x+5%13

Input :

gcd((x

`^`

2+2*x+1,x`^`

2-1)) mod 5)Output :

x%5

Note the difference with a gcd computation in ℤ[X] followed by a reduction modulo 5, input:

gcd(x

`^`

2+2*x+1,x`^`

2-1) mod 5Output :

1