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3 Answers

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4 votes

ϵ is the empty string.

Concatenation of empty string with non empty string is the string itself.

ϵ.a=a. ϵ =a

1 votes
1 votes

To generalize it lets consider r to be any regular expression.

1)   r.ε=r=ε.r  

2)   But r + ε != a if ε does not belong to the language of r i.e. L(r)

       r + ε = r if ε belongs to the language i.e. L(r)

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