document.write( "Question 762774: If the record company charges you $12 for five cds, and $20 for nine cds. How much would you pay for fifty cds. \n" ); document.write( "
Algebra.Com's Answer #464207 by Edwin McCravy(20060)\"\" \"About 
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If the record company charges you $12 for five cds, and $20 for nine cds. How much would you pay for fifty cds.
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document.write( "We must get the equation.\r\n" );
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document.write( "Let y = the total cost and x = the number of cds.\r\n" );
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document.write( "So when x = 5, y = $12 and\r\n" );
document.write( "   when x = 9, y = $20\r\n" );
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document.write( "So the problem becomes:\r\n" );
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document.write( "Find the equation of the line through the points (5,12) and (9,20)\r\n" );
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document.write( "Slope formula:\r\n" );
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document.write( "m = \"%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29\"\r\n" );
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document.write( "where (x1,y1) = (5,12)\r\n" );
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document.write( "and where (x2,y2) = (9,20)\r\n" );
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document.write( "m = \"%2820-12%29%2F%289-5%29\"\r\n" );
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document.write( "m = \"8%2F4\"\r\n" );
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document.write( "m = 2\r\n" );
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document.write( "We use the point-slope formula:\r\n" );
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document.write( "y - y1 = m(x - x1)\r\n" );
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document.write( "where (x1,y1) = (5,12) and m = 2\r\n" );
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document.write( "y - 12 = 2(x - 5)\r\n" );
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document.write( "y - 12 = 2x - 10\r\n" );
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document.write( "     y = 2x + 2\r\n" );
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document.write( "To answer:\r\n" );
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\n" ); document.write( "How much would you pay for fifty cds?
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document.write( "Substitute x = 50\r\n" );
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document.write( "     y = 2x + 2\r\n" );
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document.write( "     y = 2(50) + 2    \r\n" );
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document.write( "     y = 100 + 2\r\n" );
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document.write( "     y = 102\r\n" );
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document.write( "Answer $102.\r\n" );
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document.write( "Edwin
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