document.write( "Question 1140398: the sum of first six term of gp is -136.5 . if the common ratio is -2 . find the third term \n" ); document.write( "
Algebra.Com's Answer #760945 by ikleyn(52781)\"\" \"About 
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document.write( "Apply the formula for the sum of the first n terms of a GP\r\n" );
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document.write( "    S[6] =  \"a%2A%28%28%28-2%29%5E6-1%29%2F%28-2-1%29%29\" = \"a%2A%28%2864-1%29%2F%28-3%29%29\" = - 21a.\r\n" );
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document.write( "where \"a\" is the first term of the GP.\r\n" );
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document.write( "Therefore,  -21a = -136.5,  a = \"%28-136.5%29%2F%28-21%29\" = 6.5.\r\n" );
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document.write( "Then the third term of the GP is  \"a%5B3%5D\" = \"6.5%2A%28-2%29%5E2\" = 26.     ANSWER\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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