157 

   157 

   158   Give a regular expression that can recognise the same language as

   158   Give a regular expression that can recognise the same language as

   159   this automaton. (Hint: If you use Brzozwski's method, you can assume

   159   this automaton. (Hint: If you use Brzozwski's method, you can assume

   160   Arden's lemma which states that an equation of the form $q = q\cdot r + s$

   160   Arden's lemma which states that an equation of the form $q = q\cdot r + s$

   161   has the unique solution $q = s \cdot r^*$.)

   161   has the unique solution $q = s \cdot r^*$.)

   162 \end{enumerate}

   168 \end{enumerate}

   163 

   169 

   164 \end{document}

   170 \end{document}

   165 

   171 

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