# Does it involve \$ L_1L_2 = L_2L_1 \$ \$ L_1 = L_2?

Leave $$L_1, L_2 subseteq Sigma ^ *$$ be two languages, where $$Sigma$$ It is a finite alphabet.

Make $$L_1L_2 = L_2L_1$$ to imply $$L_1 = L_2$$?

What if $$L_1$$ Y $$L_2$$ Are they regular languages?

Can you give counterexamples?