Question

(9) For each of the following languages L, give a simple English description. Show two strings that are in L and two that are not (unless there are fewer than two strings in L or two not in L, in which case show as many as possible).

• L = {ω ∈ {a,b}∗| exactly one prefix of ω ends in a }.

• L = {ω ∈ {a,b}∗| all prefixes of ω end in a }.

• L = {ω ∈ {a,b}∗|ω = axa,x ∈ {a,b}+}.

Answer 1

1. Only one a is in the language

In language
-> a
-> bba

Not in language
-> aa
-> baba

2. Strings having only a's

In language
-> a
-> aa

Not in language
-> ab
-> baba

3. Strings that start and end with a

In language
-> aaa
-> aba

Not in language
-> ab
-> baba

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