Say that a variable A in CFG G is necessary if it appears in every derivation of some string w ∈ G. Let NECESSARY CFG = hG, Ai. a. Show that NECESSARY CFG is Turing-recognizable…

Question

Say that a variable A in CFG G is necessary if it appears in every derivation of some string w ∈ G. Let NECESSARY CFG = A is a necessary variable in G.

a. Show that NECESSARY CFG is Turing-recognizable.
b. Show that NECESSARY CFG is undecidable.

Answer 1

NECESSARY CFG is Turing-recognizable and undecidable already shown bellow

Step-by-step explanation:

Answer 2

Step-by-step explanation:

solution