Question

Which of the following pair of regular expression are not equivalent?

(a) 1(01)* and (10)*1

(b) x(xx)* and (xx)*x

(c) (ab)* and a*b*

(d) x+ and x*x+

This question was addressed to me in an internship interview.

Enquiry is from Regular Language & Expression in section Regular Expressions and Languages of Automata Theory

Answer 1

The correct option is (c) (ab)* and a*b*

For explanation: (ab)*=(a*b*)*.