document.write( "Question 1123342: The sum of the first n terms of a series is 5n^2-2n. The r-th term is...
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Algebra.Com's Answer #739652 by ikleyn(52795) $\"\"$ $\"About$

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\n" ); document.write( "The sum of the first n terms of a series is 5n^2-2n. The r’th term is...
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document.write( "The r-th term is the difference between the first r terms and the sum of the first (n-1) terms, i.e.\r\n" );
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document.write( " = (5*r^2-2*r) - (5*(r-1)^2-2*(r-1)) = \r\n" );
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document.write( "           = 5r^2 - 2r - 5r^2 + 10r - 5 + 2r - 2 = 10r - 7.\r\n" );
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document.write( "Answer.  10r - 7.  Options b).\r\n" );
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