document.write( "Question 981187: Please help I am very lost\r
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Algebra.Com's Answer #602215 by Edwin McCravy(20056)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "Please help I am very lost\r\n" );
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document.write( " 1.  EvV\r\n" );
document.write( " 2.  [(EvO)vV]>~(V>M)\r\n" );
document.write( "                   /E\r\n" );
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document.write( "This is not a valid argument.  That's because we can show that\r\n" );
document.write( "the conclusion can be false while both premises are true.\r\n" );
document.write( "We start out by putting a f above each E, that assumes\r\n" );
document.write( "the conclusion E is false.\r\n" );
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document.write( "     f\r\n" );
document.write( " 1.  EvV\r\n" );
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document.write( "       f\r\n" );
document.write( " 2.  [(EvO)vV]>~(V>M)\r\n" );
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document.write( "                    f\r\n" );
document.write( "                   /E\r\n" );
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document.write( "Now we see if we can put t's or f's above V, O and M so that both\r\n" );
document.write( "premises are true.  If so we will have found a counter-example.\r\n" );
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document.write( "The first premise can only be made true by choosing V true.  So \r\n" );
document.write( "we put t's above all the V's\r\n" );
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document.write( "     f t\r\n" );
document.write( " 1.  EvV\r\n" );
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document.write( "       f    t    t\r\n" );
document.write( " 2.  [(EvO)vV]>~(V>M)\r\n" );
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document.write( "                    f\r\n" );
document.write( "                   /E\r\n" );
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document.write( "Because V is true, [(EvO)vV] will be true regardless of \r\n" );
document.write( "what truth value we assign to O, so let's arbitrarily assign\r\n" );
document.write( "t to O.\r\n" );
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document.write( "     f t\r\n" );
document.write( " 1.  EvV\r\n" );
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document.write( "       f t  t    t\r\n" );
document.write( " 2.  [(EvO)vV]>~(V>M)\r\n" );
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document.write( "                    f\r\n" );
document.write( "                   /E\r\n" );
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document.write( "Sinve [(EvO)vV] is true, ~(V>M) must be true.\r\n" );
document.write( "That means that V>M must be false, thus M must be false.\r\n" );
document.write( "We put f above M\r\n" );
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document.write( "     f t\r\n" );
document.write( " 1.  EvV\r\n" );
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document.write( "       f t  t    t f\r\n" );
document.write( " 2.  [(EvO)vV]>~(V>M)\r\n" );
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document.write( "                    f\r\n" );
document.write( "                   /E\r\n" );
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document.write( "So as you see we have found a counter-example to this\r\n" );
document.write( "argument which shows that it is not valid.  We have exhibited\r\n" );
document.write( "a case where the conclusion is false yet the premises are\r\n" );
document.write( "both true.\r\n" );
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document.write( "If you haven't studied showing an argument invalid, then\r\n" );
document.write( "you may have copied something wrong.\r\n" );
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document.write( "Edwin
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