1. The problem statement, all variables and given/known data The idempotency theorem X∙X=X is defined for one variable, but does it apply to logic expressions with multiple variables? Example: ABC∙ABC = ABC Is this valid? 2. Relevant equations Switching algebra single-variable theorems: X+X = X X∙X = X 3. The attempt at a solution My book gives single-variable and general theorems in its switching algebra section. The single-variable theorem is listed above. The general idempotency theorems are: X+...+X = X X∙X...∙X = X However, it says nothing about whether or not the expression ABC∙ABC = ABC can be made.