document.write( "Question 1098032: The sum of the 1st and 2nd terms of an AP is 4 and the 10th term is 19
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Algebra.Com's Answer #712442 by ikleyn(52778)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "\"a%5B1%5D\" = 1;\r\n" );
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document.write( "\"a%5B2%5D\" = 3;\r\n" );
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document.write( "d = 2 (the common difference);\r\n" );
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document.write( "Check:  \"a%5B10%5D\" = \"a%5B1%5D\" + d*(10-1) = 1 + 2*9 = 19  ! Correct !\r\n" );
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document.write( "\"a%5B5%5D\" = 1 + 4*2 = 9;\r\n" );
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document.write( "\"a%5B6%5D\" = 1 + 5*2 = 11;\r\n" );
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document.write( "\"a%5B5%5D\" + \"a%5B6%5D\" = 9 + 11 = 20.\r\n" );
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\n" ); document.write( "Surely, it can be solved algebraically \r
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document.write( "\"a%5B1%5D\" + \"%28a%5B1%5D%2Bd%29\" = 4,      (1)\r\n" );
document.write( "\"a%5B10%5D\" = \"a%5B1%5D+%2B+9%2Ad\" = 19,   (2)\r\n" );
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document.write( "which gives you the system of two equations in two unknowns\r\n" );
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document.write( "\"2a%5B1%5D+%2B+d\" = 4,\r\n" );
document.write( "\"a%5B1%5D%2B9d\" = 19,\r\n" );
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document.write( "You can solve it by any method you know/you want to get the same answer.\r\n" );
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\n" ); document.write( "There is a bunch of lessons on arithmetic progressions in this site:\r
\n" ); document.write( "\n" ); document.write( "    - Arithmetic progressions\r
\n" ); document.write( "\n" ); document.write( "    - The proofs of the formulas for arithmetic progressions \r
\n" ); document.write( "\n" ); document.write( "    - Problems on arithmetic progressions \r
\n" ); document.write( "\n" ); document.write( "    - Word problems on arithmetic progressions\r
\n" ); document.write( "\n" ); document.write( "    - Solved problems on arithmetic progressions \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 \"Arithmetic progressions\".\r
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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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