# Question:Setting a variable as commutative or constant

## Question:Setting a variable as commutative or constant

Maple
Hi guys, i created a procedure to produce the commutator lie bracket, for the lie algebra so basically commutator(x,y)=x&*y-y&*x where x and y are not commutative. But there is a problem when i add constants into the mix, like a*x, a is treated as a variable. So i wonder if within the simplify function, there is a way to set certain variables/constants to be commutative or to declare a variable as a constant variable. If more information is needed check down here I am attempting to output the results of a derivation map D so say we have 2 elements of the lie algebra, x and y, and L is spanned by x and y, D(x)=ax+by and D(y)=cx+dy, where a,b,c,d are constants, so basically linear combinations of the 2 elements. Now when i place Dx into my commutator bracket, the result should be commutator(Dx,y)=commutator(cx+dy,y) and since the commutator is bilinear (that means [x+y,z]=[x,z]+[y,z] and [ax,z]=a[x,z]) commutator(cx+dy,y)=c*commutator(x,y)+d*commutator(y,y)=c(xy-yx)+d(yy-yy) c(xy-yx) but i don't get this result.
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