# Explore Our Questions

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### Every language that is reducible to a language in $\Sigma_i^p$ is also in $\Sigma_i^p$ . How?

48m ago Gilles 11.6k
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### Using the pumping lemma for a proof by contradiction

10h ago Raphael 20.4k
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### Pumping lemma on {a^n | n=3^k} — help finishing the proof

22h ago Raphael 20.4k
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### If L is a non-regular language over {a}, are all Myhill-Nerode classes singletons?

1d ago D.W. 8,724