document.write( "Question 1053935: the 10th term of an AP is -27 and the 5th term is -12. what is the 18th term. find also the sum of its 28th terms \n" ); document.write( "
Algebra.Com's Answer #669121 by ikleyn(52776)\"\" \"About 
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\n" ); document.write( "the 10th term of an AP is -27 and the 5th term is -12. what is the 18th term. find also the sum of its 28th terms
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document.write( "(1)   \"a%5B10%5D\" = \"a%5B1%5D\" + 9*d,\r\n" );
document.write( "(2)   \"a%5B5%5D\"  = \"a%5B1%5D\" + 4d.\r\n" );
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document.write( "or \r\n" );
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document.write( "(1')  -27 = \"a%5B1%5D\" + 9*d,\r\n" );
document.write( "(2')  -12  = \"a%5B1%5D\" + 4d.\r\n" );
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document.write( "Distract (2') from (1'). You will get\r\n" );
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document.write( "       -15 = 5d  --->  d = -3.\r\n" );
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document.write( "Then from (1') \"a%5B1%5D\" = -27 - 9*(-3) = -27 + 27 = 0.\r\n" );
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document.write( "Answer.  \"a%5B1%5D\" = 0,  d = -3.\r\n" );
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document.write( "         Now you can easily answer your questions.\r\n" );
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\n" ); document.write( "\n" ); document.write( "On arithmetic progressions, see the lessons\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( "    - Chocolate bars and 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
\n" ); document.write( "\"Arithmetic progressions\".\r
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