document.write( "Question 336661: If 3 < x < 7 and 4 < y < 7, which of the following best describes the range of values of x- y ?\r
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Algebra.Com's Answer #241355 by Edwin McCravy(20062)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "3 < x < 7 and 4 < y < 7\r\n" );
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document.write( "There is a rule of ADDING inequalities in the same order, that is\r\n" );
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document.write( "if A < B < C and D < E < F, then A+D < B+E < C+F\r\n" );
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document.write( "But there is NO rule for subtracting them!\r\n" );
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document.write( "But all is not lost, for we can change the second inequality \r\n" );
document.write( "to involve -y instead of +y and then we can use the addition rule.\r\n" );
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document.write( "4 < y < 7\r\n" );
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document.write( "Multiply through by -1. This will change the direction of the\r\n" );
document.write( "inequalities:\r\n" );
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document.write( "-4 > -y > -7\r\n" );
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document.write( "But then that can be written equivantly as:\r\n" );
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document.write( "-7 < -y < -4.\r\n" );
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document.write( "Now we can use the rule for adding inequalities in the same order:\r\n" );
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document.write( "  3 <  x  <  7\r\n" );
document.write( " -7 < -y  < -4 \r\n" );
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document.write( " -4 < x-y <  3\r\n" );
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document.write( "This is choice A\r\n" );
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document.write( "Edwin
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