Automata and Computability

Show that the collection of Turing-recognizable languages is closed under the operations of a. union. b. concatenation. c. star. d. intersection

Automata and Computability

Let c1 xn + c2xn-1+…+ cnx + cnx + cn + 1 be a polynomial with a root at x = x0. Let cmax be the largest absolute value of a cI . Show that (attached)

Automata and Computability

Let A = (attached) R and S are regular expressions and L(R)  L(S) . Show that A is decidable.

Automata and Computability

Let A = (attached) | R is a regular expression describing a language containing at least one string w that has 111 as a substring (i.e., w = x111y for some x and y)}. Show that A is decidable.

Automata and Computability

Let C be a language. Prove that C turing-recognizable if a decidable language D exists such that C = {x | y (x,y  D)}.