SOLUTION: Use the first eight rules of inference to complete the following proof (you may start your answer with line 4): 1. (~F v X) U (P v T) 2. F U P 3. ~P

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Question 983140: Use the first eight rules of inference to complete the following proof (you may start your answer with line 4):
1. (~F v X) U (P v T)
2. F U P
3. ~P / T
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
What are you using "U" for ? 

I will assume you are using U for "implies", "condition",
->, >, ⊃ are the symbols commonly used for that, not U.
I will use -> instead.

1. (~F v X) -> (P v T)
2. F -> P
3. ~P                       / T

4. ~P -> ~F       2, Transposition  (sometimes called "contrapositive")
5. ~F           4,3, Modus ponens
6. ~F v X         5, Addition
7. P v T        1,6, Modus ponens
8. T            7,3, Disjunctive syllogism

Edwin