278 views
2 2 votes

CONSIDER TWO PROBLEMS: $L_1$ IS A DECIDABLE LANGUAGE, AND $L_2$ IS A RECURSIVELY ENUMERABLE (R.E.) BUT NOT DECIDABLE LANGUAGE. LET $L_3$ BE ANOTHER LANGUAGE.

WHICH ONE OF THE FOLLOWING STATEMENTS IS FALSE?
 

  1. IF $L_3$ IS R.E. AND ITS COMPLEMENT $\bar{L}_3$ IS ALSO R.E., THEN $L_3$ IS DECIDABLE.
     
  2. IF $L_3$ IS REDUCIBLE TO $L_1$, THEN $L_3$ IS DECIDABLE.
     
  3. IF $L_2$ IS REDUCIBLE TO $L_3$, THEN $L_3$ IS UNDECIDABLE.
     
  4. IF $L_1$ IS REDUCIBLE TO $L_3$, THEN $L_3$ IS DECIDABLE.

1 Answer

0 0 votes

Gemini generated answer

Option D:

Reducing an easy (decidable) problem to a harder one tells us nothing about the difficulty of the harder problem. For example, any decidable language L1 can be easily reduced to the Halting Problem (which is undecidable).
Therefore, L3 could be decidable, or it could be undecidable. Asserting that L3 is decidable is incorrect.

Answer:
Position:
Show:

Related questions

4 4 votes
3 3 answers
443
443 views
GO Classes asked Nov 13, 2025
443 views
WHICH OF THE FOLLOWING LANGUAGES IS ACCEPTED BY A DETERMINISTIC PUSHDOWN AUTOMATA (DPDA)?$L_1=\left\{a^n b^n c^k \mid n, k \geq 0\right\} \cup\left\{a^i b^j c^j \mid i, j...
5 5 votes
1 1 answer
358
358 views
GO Classes asked Nov 13, 2025
358 views
CONSIDER A DFA OVER $\Sigma=\{a, b\}$ THAT ACCEPTS A STRING $w$ IF AND ONLY IF $w$ CONTAINS THE SUBSTRING "$ab$" AND ALSO ENDS WITH THE SUFFIX "$bb$".WHAT IS THE MINIMUM ...
7 7 votes
1 1 answer
310
310 views
GO Classes asked Nov 13, 2025
310 views
CONSIDER A DFA OVER $\Sigma=\{a, b\}$ THAT ACCEPTS A STRING $w$ IF AND ONLY IF $w$ SATISFIES BOTH OF THE FOLLOWING CONDITIONS:THE NUMBER OF $a^{\prime} \mathrm{S}$ IN $w$...
4 4 votes
1 1 answer
359
359 views
GO Classes asked Nov 13, 2025
359 views
Consider the machine $M^{\prime}$ : The language recognized by $M^{\prime}$ is: $\left\{w \in\{0,1\}^* \mid\right.$ $w$ HAS AN EVEN NUMBER OF $0$s AND AN EVEN NUMBER OF $...