# Subtraction of two non-homogenous monomial in a non-commutative ring

Hi every one,

I have a problem for subtracting two non-homogenous monomial "xyyx-xyx" in a unital associative free algebra with two generators x&y.

The error which is appeared is "ArithmaticError : can only subtract the elements of the same degree".

I will apreciate some one who tell me what is the soloution.

Thanks

Abdolrasoul

Actually the problem is here:

F.<x,y> = FreeAlgebra(QQ, implementation='letterplace') I=F

[xyx-2xy]*F J=F.quo(I)And the eroor is :

ArithmaticError : can only subtract the elements of the same degree"