{ "cells": [ { "cell_type": "markdown", "id": "a90ef9f8022df10e", "metadata": { "collapsed": false }, "source": [ "# Question 48\n", "Given that $A_{DFA}$ is decidable, and it will finish in a finite number of steps, we know that any DFA that accepts at least one string of finite length 3, we know that it is decidable. The algorithm is as follows:\n", "\n", "1. Start in M's start state\n", "2. Go through the symbols of w one at a time\n", "3. For all symbols of length 3, and the DFA is an accept state, we accept M DFA, otherwise reject M" ] }, { "cell_type": "markdown", "id": "2d1690ef", "metadata": {}, "source": [ "$\\pagebreak$" ] }, { "cell_type": "markdown", "id": "9a7c595f", "metadata": {}, "source": [ "# Question 49\n", "Let us assume that $EQ_{TM}$ is decidable, then we can:\n", "\n", "1. Pass two copies of $ALL_{TM}$ into $EQ_{TM}$\n", "2. If $EQ_{TM}$ accepts the two copies of $ALL_{TM}$, this means that $ALL_{TM}$ is decidable, as $EQ_{TM}$ must decide on $ALL_{TM}$\n", "3. Therefor it is impossible for $EQ_{TM}$ to be decidable given that $ALL_{TM}$ is undecidable" ] } ], "metadata": { "kernelspec": { "display_name": "Python 3", "language": "python", "name": "python3" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 2 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython2", "version": "2.7.6" } }, "nbformat": 4, "nbformat_minor": 5 }