Question

For each regular expression, give two strings that are in the corresponding language and two strings that are not.

1. (a + b)^∗ab(a + b)^∗

2. b^∗ab^∗ab^∗

3. a + (a^∗b)^∗

Comments

what is your doubt in this question?This is a very basic question.

Answer 1

1. (a + b)^∗ab(a + b)^∗

In the language : ab,aba,aaba,abab

Not in the lanugage : b,bb

2. b^∗ab^∗ab^∗

In the language : aa,aba

Not in the lanugage : a,b

3. a + (a^∗b)^∗

In the language : a,b

Not in the lanugage : All strings are in the language (Universal set)

Comments

how can u generate aaa from 3 one