0 votes 0 votes Nothing is Earthling unless it is not Alien A(x) = x is Alien E(x) = x is Earthling Which of the following is correct? (∀x)(~A(x) -> E(x)) (∀x)(E(x) -> ~A(x)) (∀x)(~A(x) <-> E(x)) Balaji Jegan asked Sep 27, 2018 Balaji Jegan 301 views answer comment Share Follow See all 4 Comments See all 4 4 Comments reply Somoshree Datta 5 commented Sep 27, 2018 reply Follow Share "Nothing is Earthling unless it is not alien" means that only if it is not an alien, then only it is an earthling. So this means that ~A(X)->E(X) (if it is not an alien, then it is an earthling) and E(X)->~A(X) (If it is an earthling, then it is not an alien) ,for all X. So option 3 is correct. 0 votes 0 votes Balaji Jegan commented Sep 27, 2018 reply Follow Share Answer given is Option 2. 0 votes 0 votes Manas Mishra commented Sep 27, 2018 reply Follow Share if u will take true case in option 3 then it will result as x is not alien and x is earthing bt its is not correct as if x is not alien then it may or may not be earthing bt if it is earthing then it should not be alien .. 0 votes 0 votes Somoshree Datta 5 commented Sep 27, 2018 reply Follow Share Yes.. I got my mistake.. If it is an earthling, then it is not an alien but if it isn't an alien doesn't imply that it is an earthling or not. So option 2 is correct. 0 votes 0 votes Please log in or register to add a comment.
Best answer 0 votes 0 votes Nothing is Earthling unless it is not Alien means if it is earthing then it should not be alien bt if not alien then it may or may not be earthing .. so (∀x)(E(x) -> ~A(x)) {if earthing then not alien is correct answer} option 2 is correct Manas Mishra answered Sep 27, 2018 • selected Sep 27, 2018 by Balaji Jegan Manas Mishra comment Share Follow See all 0 reply Please log in or register to add a comment.