Let S be a community circuit and let a ES \ {0} be an element such that a = 0. (a) Consider that then S is not a domain of integrity. (b) Show that it is 1 + a invertible. (c) You will find an example of a non-commutative circuit with a double-sided unit (ie an element 1 satisfying 1:1 = r.1= x) and some of its elements, where the previous point also applies. Let S be a community circuit and let a ES \ {0} be an element such that a = 0. (a) Consider that then S is not a domain of integrity. (b) Show that it is 1 + a invertible. (c) You will find an example of a non-commutative circuit with a double-sided unit (ie an element 1 satisfying 1:1 = r.1= x) and some of its elements, where the previous point also applies