document.write( "Question 1112775: given that the sum of the first two terms of a geometric progression is 90 and the sum to infinity is 640/7,find the two possible values of the common ratio \n" ); document.write( "

Algebra.Com's Answer #727792 by ikleyn(52795) $\"\"$ $\"About$

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document.write( "We are given   = 90,   or   = 90,   or  a = .\r\n" );
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document.write( "We are also given that   = ,   or   a = .\r\n" );
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document.write( "Since left sides of the two last equations are identical, their right sides are equal:\r\n" );
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document.write( " = ,\r\n" );
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document.write( "which implies\r\n" );
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document.write( "90*7 = ,\r\n" );
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document.write( "63 =    ====>   = 64 - 63 = 1  ====>   =   ====>  r = +/-  = +/- .\r\n" );
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document.write( "Answer.  The two value of the common ratio are  +/-.\r\n" );
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