maths_mocktest1_11

Question

Answer 1

A + B, is satisfiable when either A or B is 1. But not tautology. as both A and B can 0.

A tautology means any assignment to variables produces a 1. So, it is trivially satisfiable.

A contradiction means any assignment ot variables produces a 0. So, it can never be satisfied.

Coming to B option, it says Every satisfiable formula is not tautology. This is wrong as valid formula is both satisfiable as well as tautology. If we change "every" to "some", B option becomes correct. Actually this sentence is not grammatically correct and can also be interpreted as "Every satisfiable formula is not a tautology" meaning some satsfiable formula is not tautology. In this case B option becomes TRUE. 

Comments

y cnt treat in positive manner every Every satisfiable  is not a tautology. it means they want to say some satisfiable is contegency y cnt treat like this ?????

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You are correct. "not a tautology" makes it as you said. "not tautology" is slightly ambiguous. I have edited the answer.

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thanks sir ...