document.write( "Question 1186348: Determine how many rows are in the corner section of a stadium containing 3920 seats if the
\n" ); document.write( "first row has 10 seats and each successive row has 6 additional seats? \n" ); document.write( "
Algebra.Com's Answer #817242 by ikleyn(52810)\"\" \"About 
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document.write( "It is about finding the number of terms of an arithmetic progression, when its\r\n" );
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document.write( "first term, the common difference and the sum of n terms are given.\r\n" );
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document.write( "The formula for the sum of n first terms of an AP is\r\n" );
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document.write( "    \"S%5Bn%5D\" = \"%28a%5B1%5D+%2B+%28d%2A%28n-1%29%29%2F2%29%2An%29\",\r\n" );
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document.write( "In this problem,  \"a%5B1%5D\" = 10,  d = 6.  So your equation is\r\n" );
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document.write( "    \"%2810+%2B+%286%2A%28n-1%29%29%2F2%29%2An\" = 3920.\r\n" );
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document.write( "Multiply both sides by 2\r\n" );
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document.write( "    (20 + 6*(n-1))*n = 7840\r\n" );
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document.write( "    20n + 6n^2 - 6n = 7840\r\n" );
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document.write( "     6n^2 + 14n - 7840 = 0.\r\n" );
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document.write( "Apply the quadratic formula and find the roots.\r\n" );
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document.write( "You will get two roots. One root is negative, and we reject it.\r\n" );
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document.write( "The other root is positive, and its value is  35.\r\n" );
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document.write( "It is the solution to the problem.\r\n" );
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document.write( "ANSWER.  35 rows.\r\n" );
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\n" ); document.write( "\n" ); document.write( "On geometric progressions,  see introductory lessons\r
\n" ); document.write( "\n" ); document.write( "    - Geometric progressions\r
\n" ); document.write( "\n" ); document.write( "    - The proofs of the formulas for geometric progressions \r
\n" ); document.write( "\n" ); document.write( "    - Problems on geometric progressions\r
\n" ); document.write( "\n" ); document.write( "    - Word problems on geometric progressions\r
\n" ); document.write( "\n" ); document.write( "in this site.\r
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\n" ); document.write( "\n" ); document.write( "Also,  you have this free of charge online textbook in ALGEBRA-II in this site\r
\n" ); document.write( "\n" ); document.write( "    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.\r
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\n" ); document.write( "\n" ); document.write( "The referred lessons are the part of this online textbook under the topic
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\n" ); document.write( "\n" ); document.write( "Save the link to this textbook together with its description\r
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\n" ); document.write( "\n" ); document.write( "Free of charge online textbook in ALGEBRA-II
\n" ); document.write( "https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson\r
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\n" ); document.write( "\n" ); document.write( "into your archive and use when it is needed.\r
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