Tagged Questions

Regular expressions or Regex is a search pattern for strings defined by a sequence of characters.

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regex patterns not working [on hold]

i am using this regex ^[[ \w\.\,\-\$\€\&]* ({[\w]+\:[\w]+})* ({=[\w ]+\.[\w]+})*]*$ and i want to match paterns like this ...
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Factorising Cyclic expression .

What are ways for factorising cyclic expressions? Note: I am not saying about specific one. Just ways of factorising cyclic expressions.
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Finding LCM of an expression

Image link I am currently trying to figure out how to solve this problem. I know how they got the denominator but am unsure how they got 6x in the numerator? Can somebody explain this to me?
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Write each of the following languages from the alphabet is ∑ = {0, 1} as a regular expression:? [closed]

a) All even length strings that end with 0 b) All odd length strings with a 0 in the middle. c)Strings that are divisible to 3 when interpreted as a positive binary number(for ex.,0011,001001,1100,...
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Express the function $f(x)= (1-\sin x)/(1+\sin x)$ as the sum of an even and odd function. [closed]

Express the function $f(x)= (1-\sin x)/(1+\sin x)$ as the sum of an even and odd function.
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equivalent regular expr

Given a regular expression $r_1$, is $(r_1^*)^* = (r_1^*)$. I know that this is true but I do not know how to prove it. Would it be adequate to set $r_1$ to a regular expression such as $(a+b)$ for ...
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Use regular algebra to prove that (a + ab)*a = a(a + ba)* [closed]

I don't see how it's possible to reverse ab to ba.
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relation on Languages of one finite machine !?

I adopted this question from 2013 Final Entrance Exam on CS. We have Finite Machine $M$ and Languages $L_1$ to $L_4$ as depicted in following picture: The question is which of the $A$ to $D$ ...
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If $A^{2x}=4$ what is ${A^{3x}-A^{-3x}\over A^x - A^{-x}}$

If $A^{2x}=4$ and $A > 0$, what is the numerical value of $${A^{3x}-A^{-3x}\over A^x - A^{-x}}$$ Could anyone find the solution and answer? Thanks
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Language with middle third removed

Originating from Sipser's book: Let $A$ be any language, define $A_{{1\over3}-{1\over3}}$ be the subset of strings of $A$ whose middle third is removed. The solution I came across makes the ...
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Is there a subtle difference between NOEXTEND(A) vs NOPREFIX(A)?

My question originates from Sipser's book. Let A be a language with the DFA $(Q, \Sigma, \delta, q_{0}, F)$ and define: NOPREFIX(A) = {w $\in$ A| no proper prefix of w is a member of A} NOEXTEND(A) ...
I am working through a lecture and it constructs a DFA using the language: $$\{w\mid w\textsf{ is any string not in }(ab^+)^\ast\}$$ What does the $(ab^+)$ mean?