document.write( "Question 331346: The third and fourth terms of a sequence are 26 and 40. If the second differences are a constant 4, what are the first five terms of the sequence?
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Algebra.Com's Answer #237480 by Edwin McCravy(20056)\"\" \"About 
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The third and fourth terms of a sequence are 26 and 40. If the second differences are a constant 4, what are the first five terms of the sequence?
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document.write( "     1st          2nd\r\n" );
document.write( "an  diffs        diffs    \r\n" );
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document.write( "a1 |       |\r\n" );
document.write( "   | a2-a1 |\r\n" );
document.write( "a2 |       | (26-a2)-(a2-a1) = 26-a2-a2+a1 = 26-2a2+a1 = 4, or a1-2a2=-22\r\n" );
document.write( "   | 26-a2 |\r\n" );
document.write( "26 |       | 14-(26-a2) = 14-26+a2 = -12+a2 = 4, or a2=16\r\n" );
document.write( "   |  14   |\r\n" );
document.write( "40 |       | a5-40-14 = a5-54 = 4, or a5 = 58\r\n" );
document.write( "   | a5-40 |\r\n" );
document.write( "a5 |       |\r\n" );
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document.write( "So we have the system of equations:\r\n" );
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document.write( "\"system%28a%5B1%5D-2a%5B2%5D=-22%2C+a%5B2%5D=16%2C+a%5B5%5D=58%29\"\r\n" );
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document.write( "Susbstitute 16 for \"a%5B2%5D\" in the first equation:\r\n" );
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document.write( "\"a%5B1%5D-2a%5B2%5D=-22\"\r\n" );
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document.write( "\"a%5B1%5D-2%2816%29=-22\"\r\n" );
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document.write( "\"a%5B1%5D-32=-22\"\r\n" );
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document.write( "\"a%5B1%5D=10\"\r\n" );
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document.write( "So \"a%5B1%5D=10\", \"a%5B2%5D=16\", \"a%5B3%5D=26\", \"a%5B4%5D=40\", \"a%5B5%5D=58\"\r\n" );
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document.write( "Checking:\r\n" );
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document.write( "   1st 2nd \r\n" );
document.write( "   dif dif\r\n" );
document.write( "10\r\n" );
document.write( "    6\r\n" );
document.write( "16      4\r\n" );
document.write( "    10 \r\n" );
document.write( "26      4\r\n" );
document.write( "    14\r\n" );
document.write( "40      4\r\n" );
document.write( "    18 \r\n" );
document.write( "58\r\n" );
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document.write( "Edwin
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