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)