Which of the following is not a regular expression?

Related Questions

• A language is represented by a regular expression (a)*(a + ba). Which of the following strings does not belong to the regular set represented by the above expression?
• Let P be a regular language and Q be context-free language such that Q ∈ P. (For example, let P be the language represented by the regular expression p*q* and Q be {pnqn n∈ N}). Then which of the following is ALWAYS regular?
• If a language is denoted by a regular expression L = ( x )* (x y x ), then which of the following is not a legal string within L ?
• Which of the following are decidable? 1) Whether the intersection of two regular language is infinite. 2) Whether a given context free language is regular. 3) Whether two push down automata accept the same language. 4) Whether a given grammar is context free.
• Languages are proved to be regular or non regular using pumping lemma.
• Which one of the following languages over the alphabet {0,1} is described by the regular expression: (0+1)*0(0+1)*0(0+1)*?
• Which of the following regular expression identity is true?
• Consider the following Finite State Automaton The language accepted by this automaton is given by the regular expression
• Let L={w (0 + 1)* w has even number of 1s}, i.e. L is the set of all bit strings with even number of 1s. Which one of the regular expression below represents L?
• The regular expression have all strings in which any number of 0’s is followed by any number of 1’s followed by any number of 2’s is :