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Q

choose incorrect identity from the following

a) (a+b)* = (a+b)*(a+b)*

b) (a+b)* = a(a+b)*b(a+b)* + ∈

c)(a+b)* = (a+b)*ab(a+b)* + b*a*

d)None of the above

correct answer given is option D but obviously option B and option C both are wrong too. 

2 Answers

Best answer
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Yes option B is wrong .


We can not produced string ba from option B. [Even a,b cannot be derived]

But

option C is right . [all string over {a,b} contain sub string "ab" + all string doesn't contain "ab" as sub-string = all strings over {a,b}]

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Hard and Fast Rule is to do such quest is try to derive smallest strings from L.H.S AND R.H.S.

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