Question

The meaning of the regular expression (a+b)(a+b) is

A)Strings of a's and b's where length is 2

B)Strings of a's and b's of any length.

C)Null string

D)None

Comments

Ans A)

Answer 1

A)Strings of a's and b's where length is 2  $\Rightarrow$ (a+b) (a+b)

B)Strings of a's and b's of any length     $\Rightarrow$  (a+b)^* ≡ (a^*+b)^* ≡ (a+b^*)^*≡ (a^*+b^*)^*

C)Null String $\Rightarrow$ {∈}

Hence,Option(A)Strings of a's and b's where length is 2 is the correct choice.

Comments

Say if the string is ab, ba I agree "Strings of a AND B where length 2". what about string like aa, bb Can I say " strings of a's and b's in this case"? Doubt may be silly..please clarify.!

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Here Strings of a's and b's where length is 2 means " String of  length 2 where input Symbols ∑ ={a,b}.

Here Regular Expression (a+b)(a+b) can accept all string of length 2 (aa,ab,ba,bb).

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Thank you!