document.write( "Question 849942: The first term of a geometric sequence is 3. The sum of the first three terms is 129. Find the possible values of the common ratio. \n" ); document.write( "
Algebra.Com's Answer #511871 by AnlytcPhil(1806)\"\" \"About 
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The first term of a geometric sequence is 3.\r
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document.write( "   a1 + a2 + a3 = 129\r\n" );
document.write( "a1 + a1r + a1rē = 129\r\n" );
document.write( "   3 + 3r + 3rē = 129\r\n" );
document.write( " 3rē + 3r - 126 = 0\r\n" );
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document.write( "Divide every term by 3\r\n" );
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document.write( "    rē + r - 42 = 0\r\n" );
document.write( "     (r+7)(r-6) = 0\r\n" );
document.write( "    r+7=0; r-6=0 \r\n" );
document.write( "     r=-7;  r=6\r\n" );
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document.write( "Those are the two possible values of the common ratio. \r\n" );
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document.write( "Checking:\r\n" );
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document.write( "So the sequence could be either 3, -21, 147, -1029, 7203, ...\r\n" );
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document.write( "The sum of the first three terms is 3-21+147 = 129\r\n" );
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document.write( "or it could be 3, 18, 108, 648, 3888, ...\r\n" );
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document.write( "The sum of the first three terms is 3+18+108 = 129\r\n" );
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document.write( "Edwin
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