5.1 Reducibility (continued)



















Prove that the language is Undecidable.

	L2 = { <M> | M is a TM and M accepts the string 1001
	       (note that M could accept other strings as well) }

What problem will you reduce to L2?

How can you use an L2 decider to decide A[TM]?
Perhaps you could run the L2 decider R with <M> as input?
Will this tell you anything?


What machine can you give to an L2 decider
so if the L2 decider accepts you know M accepts w?

Use an L2 decider R to build an A[TM] decider S.

Write the proof that L2 is Undecidable.



















Classwork
You may work with a partner.

Prove that the language is Undecidable.


	A = { <M> | M is a TM which accepts some string of 1s and 0s
				containing an odd number of 1s }