document.write( "Question 1141206: (G • S) → D
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Algebra.Com's Answer #762125 by Edwin McCravy(20055)\"\" \"About 
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document.write( "1. (G • S) → D\r\n" );
document.write( "2. (S → D) → P\r\n" );
document.write( "3. G                                 /P\r\n" );
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document.write( "                       | 4. ~P         Assumption for indirect proof\r\n" );
document.write( "                       | 5. ~(S → D)   2,4, Modus tollens\r\n" );
document.write( "                       | 6. ~(~S v D)  5, Material implication\r\n" );
document.write( "                       | 7. ~~S • ~D   6, deMorgan's law\r\n" );
document.write( "                       | 8. S • ~D     7, double negation\r\n" );
document.write( "                       | 9. ~D • S     8, commutation\r\n" );
document.write( "                       |10. ~D         9, simplification\r\n" );
document.write( "                       |11. ~(G • S)   1,10, Modus tollens\r\n" );
document.write( "                       |12. ~G v ~S    11, deMorgan's law\r\n" );
document.write( "                       |13. S • ~D     9, commutation\r\n" );
document.write( "                       |14. S          13, simplification\r\n" );
document.write( "                       |15. ~S v ~G    12, commutation\r\n" );
document.write( "                       |16. ~~S        14,  double negation\r\n" );
document.write( "                       |17. ~G         15,16 disjunctive syllogism\r\n" );
document.write( "                       |18. G • ~G     2,17 conjunction \r\n" );
document.write( "19. P                Lines 4-18 for indirect proof\r\n" );
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document.write( "Edwin

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