0 votes 0 votes Show that the following problem is undecidable. Given any Turing machine $M, a\in \Gamma $ and $w \in \Sigma^{+}$, determine whether or not the symbol $a$ is ever written when $M$ is applied to $w$. Theory of Computation peter-linz peter-linz-edition5 theory-of-computation decidability proof + – Rishi yadav asked Mar 14, 2019 • retagged Mar 15, 2019 by Rishi yadav Rishi yadav 130 views answer comment Share Follow See all 0 reply Please log in or register to add a comment.