0 votes 0 votes Lets S1 and S2 be two algebric structure : S1 : {0,1,2,3,4,….,m-1},+m-1 S2 : {0,1,2,3,4,….,m-2},+m-1 +m is the addition modulo m. Which of the following are Groups ? Mathematical Logic group-theory discrete-mathematics + – Na462 asked Dec 8, 2018 Na462 402 views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply Na462 commented Dec 8, 2018 reply Follow Share I get it for S2, but little confused why S1 IS WRONG ? 0 votes 0 votes himgta commented Dec 8, 2018 reply Follow Share consider S1={0,1,2,3} on addition mudulo 3 then you can check that identity element does not exist 0 (addition mpdulo 3) 3 is 0 here...not 3 1 votes 1 votes Please log in or register to add a comment.