document.write( "Question 872011: Write each series in summation notation.\r
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Algebra.Com's Answer #525855 by Edwin McCravy(20056)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "You recognize them as the first 5 powers of 2 with alternating signs,\r\n" );
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document.write( "which is the same as the first 5 powers of -2, that is,\r\n" );
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document.write( "(-2)1 + (-2)2 + (-2)3 + (-2)4 + (-2)5 \r\n" );
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document.write( "You can choose any letter as an \"index\" or \"dummy variable\", I'll\r\n" );
document.write( "choose the letter k, but you can choose any letter:\r\n" );
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document.write( "\"sum%28%28-2%29%5Ek%2Ck=1%2Cmatrix%281%2C3%2C%22%22%2C%22%22%2C5%29%29\"\r\n" );
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document.write( "Very often when the signs alternate, a factor of (-1)k is preferred.\r\n" );
document.write( "In that case you would write (-2)k as (-1)k2k, and write the summation as:\r\n" );
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document.write( "\"sum%28%28-1%29%5Ek%2A2%5Ek%2Ck=1%2Cmatrix%281%2C3%2C%22%22%2C%22%22%2C5%29%29\"\r\n" );
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document.write( "Edwin
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