document.write( "Question 1109080: Find the S20 if T3 = 19 and T8 = 44. \n" ); document.write( "
Algebra.Com's Answer #724098 by ikleyn(52786)\"\" \"About 
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document.write( "There are 8-3 = 5 common differences between T3= 19  and  T8= 44, i.e.\r\n" );
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document.write( "5d = 44 - 19 = 25  ====>  d = \"25%2F5\" = 5.\r\n" );
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document.write( "Hence,  \"T%5B1%5D\" = \"T%5B3%5D+-+2d\" = 19-2*5 = 9.\r\n" );
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document.write( "Then \"T%5B20%5D\" = \"T%5B1%5D%2B19%2A5\" = 9 + 5*19 = 104.\r\n" );
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document.write( "It implies  \"S%5B20%5D\" = \"%28%28T%5B1%5D%2BT%5B20%5D%29%2F2%29%2A20\" = \"%28%289%2B104%29%2F2%29%2A20\" = 113*10 = 1130.\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( "    - Mathematical induction and arithmetic progressions\r
\n" ); document.write( "\n" ); document.write( "    - One characteristic property of 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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