Euclidean remainder : rem

rem returns the euclidean remainder between two polynomials (decreasing power division). If the polynomials are represented as expressions, the variable may be specified as a third argument.
Input :

rem(x^3-1,x^2-1)

Output :

x-1

To have the remainder of x² + 2x + 4 by x² + x + 2 we can also input :

rem([1,2,4],[1,1,2])

Output :

[1,2]

i.e. le polynomial x + 2.