Question 1125684:  Choose one of the proofs below and use one of the indirect proof techniques (reductio ad absurdum or conditional proof) presented in Chapter 8 to demonstrate the validity of the argument. The proofs below may use any of the rules of inference or replacement rules given in Chapter 8.
 
(G • P) → K, E → Z, ~P → ~ Z, G → (E v L), therefore, (G • ~L) → K 
(S v T) ↔ ~E, S → (F • ~G), A → W, T → ~W, therefore, (~E • A) → ~G 
(S v T) v (U v W), therefore, (U v T) v (S v W) 
~Q → (L → F), Q → ~A, F → B, L, therefore, ~A v B 
~S → (F → L), F → (L → P), therefore, ~S → (F → P) 
 
 Answer by jim_thompson5910(35256)      (Show Source): 
You can  put this solution on YOUR website!  
I'm going to pick on the first line  
(G • P) → K, E → Z, ~P → ~ Z, G → (E v L), therefore, (G • ~L) → K 
to prove that out. 
 
 
I'll do so in two ways. The first of which is through a conditional proof
 
 
Start with the antecedent of the conclusion, which is (G & ~L) and show how it leads to K 
 
 
note: I used an ampersand in place of a dot
 
 
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Then I'll show how to do a proof by contradiction (aka reductio ad absurdum), which is an indirect proof. 
 
 
The idea is to assume the complete opposite the conclusion, and then show how a contradiction arises. 
  
 
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