document.write( "Question 202838: Algebra 2 worksheet on Arithmetic sequence\r
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Algebra.Com's Answer #153031 by Edwin McCravy(20062) $\"\"$ $\"About$

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The third term of an arithmetic sequence is 9 and the seventh term is 31. Find the sum of the first twenty-two terms.
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document.write( "___, ___,  9 , ___, ___, ___,  31, ...\r\n" );
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document.write( "The nth term formula is\r\n" );
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document.write( "Substitute  in\r\n" );
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document.write( "Substitute \r\n" );
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document.write( "Now Substitute  in\r\n" );
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document.write( "Substitute \r\n" );
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document.write( "So we have the system:\r\n" );
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document.write( "Solve the first equation for \r\n" );
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document.write( "Substitute  in the second equation:\r\n" );
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document.write( "Substituting  in\r\n" );
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document.write( "Now we can use the formula for the sum of the\r\n" );
document.write( "first n terms:\r\n" );
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document.write( "Substitute , , \r\n" );
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\n" ); document.write( "How many terms of the arithmetic sequence 2,4,6,8, ... add up to 60,762
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document.write( "Subtract any two consecutive terms and get \r\n" );
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document.write( " = the first term, which is , and \r\n" );
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document.write( "Multiply both sides by 2:\r\n" );
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document.write( "Divide through by 2\r\n" );
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document.write( "Factor:\r\n" );
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document.write( " or \r\n" );
document.write( " or \r\n" );
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document.write( "We discard the negative answer, and so\r\n" );
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document.write( "Edwin

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