u = - x
The symbol - is used as notation for the Ext-algebra negation.
i1 : L = lieAlgebra{a,b,c}/{a b,b c} o1 = L o1 : LieAlgebra
i2 : E = extAlgebra(3,L) o2 = E o2 : ExtAlgebra
i3 : -(2 ext_3-ext_4) o3 = - 2ext_3 + ext_4 o3 : E