Which one of the following Boolean expressions is NOT a tautology?
No,you are not correct.Conditional statement P->q is false only when p is true and q is false and true otherwise.
You can also check in this way-
Hence,(a∧b∧c)→(c∨a) is tautology.
@ Aayushi ,
:= ab` + bc` + a` + c continuing ...
= a'+ab' + c+c'b
= a'+b' + c+b for details see this http://cs.stackexchange.com/questions/24587/which-law-is-this-expression-x-x-y-xy
= a'+c + b+b'
= a'+c + 1
= 1 (Tautology)
LeenSharma putting 0/1 can be time consuming because we may have to check all the combination and that can be frustrating in exam.
All doubts are cleared.Nice explanation.
option B reduces to A+B rest all reduces to 1
Hence, B is not a tautology.