How to prove that if a language A is not regular then A* isn't regular either?
I have tried the usual methods with no result.
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Sign up to join this communityHow to prove that if a language A is not regular then A* isn't regular either?
I have tried the usual methods with no result.
Hint: Suppose $L$ is any language over the alphabet $\Sigma$. If $L$ is not regular then so is $L+\Sigma$, yet $(L+\Sigma)^* = \Sigma^*$ is regular.