If L1 is regular L2 is unknown but L1-L2 is regular ,then L2 must be ans.Empty setCFGDecidableRegular

The statement "If L1 is regular L2 is unknown but L1-L2 is regular, then L2 must be" is a question related to formal language theory in computer science, particularly the theory of regular languages.

Here's a step-by-step analysis:

1. L1 is a regular language. By definition, a regular language is a language that can be expressed with a regular expression or a deterministic or non-deterministic finite automaton.

2. L2 is an unknown language. We don't have any information about whether it's regular, context-free, context-sensitive, etc.

3. L1 - L2 is regular. This means that the language formed by all the strings that are in L1 but not in L2 is a regular language.

Given these conditions, we cannot definitively determine the nature of L2. L2 could be a regular language, a context-free language, or any other type of language. The subtraction operation (L1 - L2) does not provide enough information to determine the properties of L2.

So, the answer is that we cannot definitively say what L2 is based on the given information. It could be any type of language.