document.write( "Question 396669: Write 2 - 4 + 8 - 16 + ... + 128 using sigma notation. \n" ); document.write( "
Algebra.Com's Answer #281328 by ewatrrr(24785)\"\" \"About 
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document.write( "\"a%5Bn%5D+=+2%2A%28-2%29%5E%28n-1%29++\"
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document.write( "\"a%5B5%5D+=+2%2A%28-2%29%5E%28n-1%29+=+32+\"
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document.write( "\"a%5B6%5D+=+2%2A%28-2%29%5E%28n-1%29+=+-64+\"
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document.write( "\"a%5B7%5D+=+2%2A%28-2%29%5E%28n-1%29+=+128++\"\r
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document.write( "\"sum%28++2%2A%28-2%29%5E%28n-1%29+%2C+n=1%2C+7+%29\" \n" );
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