SOLUTION: Proof: 1. ~O > ~ O 2. X > (X > O) /~X

Algebra.Com
Question 1090652: Proof:
1. ~O > ~ O
2. X > (X > O)
/~X

Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!

The argument is Invalid

How can we determine this? By use of a logic table shown below

Breakdown of the table


Row 2, where I've marked the premises and conclusion in red, shows us that the argument is invalid. This row is a case where all of the premises are true but the conclusion is false.

In short,
if O = true and X = true
then...
the premise ~O > ~O is true
the premise X > (X > O) is true
but the conclusion ~X is false

This is why the argument is invalid. It is impossible to do a proof derivation of invalid proofs. It's possible your teacher made a typo or s/he is trying to throw a trick question.

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