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Let $R_{1}$ and $R_{2}$ be regular sets defined over the alphabet $\Sigma$ Then:

  1. $R_{1} \cap R_{2}$ is not regular.
  2. $R_{1} \cup R_{2}$ is regular.
  3. $\Sigma^{*}-R_{1}$ is regular.
  4. $R_{1}^{*}$ is not regular.
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3 Answers

Best answer
33 votes
33 votes

Regular Languages are closed under

  1. Intersection
  2. Union
  3. Complement
  4. Kleen-Closure

$\Sigma^∗−R_1$ is the complement of $R_1$
 

Correct Options: B;C

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  1. R1 ∩ R2 is not regular.-FALSE,Regular sets are closed under Intersection
  2. R1 ∪ R2 is regular. TRUE,Regular sets are closed under Union
  3. −R1 is regular,TRUE,Regular sets are closed under Complement
  4. R1* is not regular.FALSE,Regular sets are closed under Intersection
1 votes
1 votes
Everything is true if they have not used the word not in the question.
Answer:

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