document.write( "Question 902538: If x = -1, find the value of 2013x^2013 + 2012x^2012 + 2011x^2011 + 2010x^2010 + . . . + 2x^2 + x.\r
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Algebra.Com's Answer #547397 by Theo(13342)![]() ![]() You can put this solution on YOUR website! i'm not sure if this is the way you're supposed to solve this, but i do believe i did solve it.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "it doesn't look like an arithmetic series or a geometric series so those formulas don't appear to work with this.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the first term is x \n" ); document.write( "the second term is 2x^2 \n" ); document.write( "the third term is presumably 3x^3 \n" ); document.write( "the fourth term is presumably 4x^4 \n" ); document.write( "the 2013th term is 2013x^2013 as shown.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "when x = -1, this turns out to be:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "first term is -1 \n" ); document.write( "second term is 2 \n" ); document.write( "third term is -3 \n" ); document.write( "fourth term is 4 \n" ); document.write( "etc.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "i then looked for a pattern. \n" ); document.write( "the pattern i found is shown here.\r \n" ); document.write( "\n" ); document.write( " \r\n" ); document.write( "n An Sn\r\n" ); document.write( "1 -1 -1\r\n" ); document.write( "2 2 1\r\n" ); document.write( "\r\n" ); document.write( "3 -3 -2\r\n" ); document.write( "4 4 2\r\n" ); document.write( "\r\n" ); document.write( "5 -5 -3\r\n" ); document.write( "6 6 3\r\n" ); document.write( "\r\n" ); document.write( "7 -7 -4\r\n" ); document.write( "8 8 4\r\n" ); document.write( "\r\n" ); document.write( "9 -9 -5\r\n" ); document.write( "10 10 5\r\n" ); document.write( "\r\n" ); document.write( "11 -11 -6\r\n" ); document.write( "12 12 6\r\n" ); document.write( "\r\n" ); document.write( "13 -13 -7\r\n" ); document.write( "14 14 7\r\n" ); document.write( "\r\n" ); document.write( "15 -15 -8\r\n" ); document.write( "16 16 8\r\n" ); document.write( "\r\n" ); document.write( "17 -17 -9\r\n" ); document.write( "18 18 9\r\n" ); document.write( "\r\n" ); document.write( "19 -19 -10\r\n" ); document.write( "20 20 10\r\n" ); document.write( "\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "n is the term in the series. \n" ); document.write( "An is the nth term in the series. \n" ); document.write( "Sn is the sum of the n terms in the series.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "if you look at the series, you will see that the sum of n terms, where n is even, is equal to exactly one half of the nth term.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the sum of 16 terms is 8 \n" ); document.write( "the sum of 18 terms is 9 \n" ); document.write( "the sum of 20 terms is 10\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "if you look at the sum of the odd terms, you will see that the sum of the n terms, where n is odd, is equal to the negative of the sum of the n+1 terms.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the sum of 15 terms is -8 \n" ); document.write( "the sum of 17 terms is -9 \n" ); document.write( "the sum of 19 terms is -10\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "you can extrapolate from this to get the sum of 2013 terms as follows.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the sum of 2014 terms is 1007 \n" ); document.write( "therefore the sum of 2013 terms is -1007.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "that should be your answer.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "i confirmed using excel that this is the case so i'm reasonably confident this is the answer you are looking for unless i completely misinterpreted the problem.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |