List all strings over X a b c of length 2 Let alpha abba b

List all strings over X = {a, b, c} of length 2. Let alpha = abba, beta = cbbab, compute the following (a) beta alpha (b) alpha beta (c) |beta beta| Let X = {ab, bc, ba}. In each part, tell whether the string belongs to X^+ (the set of all strings over X). (a) abda (b) abbbcba (c) abbcbaba

Solution

2. Strings of length 2:

aa, ba, ca

ab, bb, cb

ac, bc, cc

3. = abba =cbbab

i) = cbbababba=cbbabba

ii) = abbacbbab

iii) //=/cbbabcbbab/= cbbab