document.write( "Question 766413: which set of ordered pairs is a function
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Algebra.Com's Answer #466866 by Edwin McCravy(20081)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "Rule:\r\n" );
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document.write( "Make a list of all first coordinates\r\n" );
document.write( "If the list contains any number more than once it is NOT a function\r\n" );
document.write( "If the list contains each number once only, it is a function.\r\n" );
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document.write( "Note: [It does not matter whether any of the second coordinates are \r\n" );
document.write( "the same or not, only the first coordinates matter.]\r\n" );
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document.write( "(1,2)(3,4)(5,6)(3,-4)\r\n" );
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document.write( "That one is not a function because the list of first coordinates 1,3,5,3\r\n" );
document.write( "contains 3 more than once, in this case twice.\r\n" );
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document.write( "(8,4)(4,3)(2,2)(8,1)\r\n" );
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document.write( "That one is not a function because the list of first coordinates 8,4,2,8,\r\n" );
document.write( "contains 8 more than once, in this case twice.\r\n" );
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document.write( "(2,5)(3,10)(4,15)(5,20)\r\n" );
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document.write( "That one is a function because the list of first coordinates 2,3,4,5, does\r\n" );
document.write( "not contain the same number twice.\r\n" );
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document.write( "(2,4)(2,3)(2,1)(2,0)\r\n" );
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document.write( "That one is not a function because the list of first coordinates 2,2,2,2,\r\n" );
document.write( "contains 2 more than once, in this case four times.\r\n" );
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document.write( "Edwin
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