document.write( "Question 957592: If the first 3 items of a geometric progression are a − 1, a +3, and 3 a +1 for some positive
\n" ); document.write( "number a, what is the numerical value of the fourth term?
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Algebra.Com's Answer #585177 by MathLover1(20850)\"\" \"About 
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given:\r
\n" ); document.write( "\n" ); document.write( "the first \"3\" terms of a geometric progression are
\n" ); document.write( "\"a-1\",
\n" ); document.write( "\"a+%2B3\", and
\n" ); document.write( "\"3a+%2B1\"
\n" ); document.write( "for some positive number \"a\"\r
\n" ); document.write( "\n" ); document.write( "In a Geometric Sequence each term is found by \"multiplying\" the previous term by a \"constant\". \r
\n" ); document.write( "\n" ); document.write( "Let a \"constant\" be \"k\":\r
\n" ); document.write( "\n" ); document.write( "\"%28a+-1%29k=+a+%2B3\"\r
\n" ); document.write( "\n" ); document.write( "\"k=+%28a+%2B3%29%2F%28a+-1%29\"..........(1)\r
\n" ); document.write( "\n" ); document.write( "\"%28a+%2B3%29k=+3a+%2B1\"\r
\n" ); document.write( "\n" ); document.write( "\"k=+%283a+%2B1%29%2F%28a+%2B3%29\"..........(2)\r
\n" ); document.write( "\n" ); document.write( "make \"%281%29=%282%29\"\r
\n" ); document.write( "\n" ); document.write( "\"%28a+%2B3%29%2F%28a+-1%29=%283a+%2B1%29%2F%28a+%2B3%29\" ............cross multiply\r
\n" ); document.write( "\n" ); document.write( "\"%28a+%2B3%29%28a+%2B3%29=%283a+%2B1%29%28a+-1%29\"\r
\n" ); document.write( "\n" ); document.write( "\"a%5E2+%2B3a+%2B3a%2B9=3a%5E2-3a+%2Ba+-1\"\r
\n" ); document.write( "\n" ); document.write( "\"a%5E2+%2B6a%2B9=3a%5E2-2a+-1\"\r
\n" ); document.write( "\n" ); document.write( "\"0=3a%5E2-2a+-1-a%5E2+-6a-9\"\r
\n" ); document.write( "\n" ); document.write( "\"2a%5E2-8a+-10+=0\"........simplify\r
\n" ); document.write( "\n" ); document.write( "\"a%5E2-4a+-5=0\"\r
\n" ); document.write( "\n" ); document.write( "\"a%5E2%2Ba-5a+-5=0\"\r
\n" ); document.write( "\n" ); document.write( "\"%28a%5E2%2Ba%29-%285a+%2B5%29=0\"\r
\n" ); document.write( "\n" ); document.write( "\"a%28a%2B1%29-5%28a+%2B1%29=0\"\r
\n" ); document.write( "\n" ); document.write( "\"%28a-5%29%28a+%2B1%29=0\"\r
\n" ); document.write( "\n" ); document.write( "solutions:\r
\n" ); document.write( "\n" ); document.write( "\"a=5\"\r
\n" ); document.write( "\n" ); document.write( "or \r
\n" ); document.write( "\n" ); document.write( "\"a=-1\"\r
\n" ); document.write( "\n" ); document.write( "since given that first 3 terms are \"a+-1\", \"a+%2B3\", and \"3a+%2B1\" for some \"positive\"
\n" ); document.write( "number \"a\", our solution is \"a=5\"\r
\n" ); document.write( "\n" ); document.write( "so, your terms are:
\n" ); document.write( "\"a+-1=5-1=4\",
\n" ); document.write( "\"a+%2B3=5%2B8=8\", and
\n" ); document.write( "\"3a+%2B1=3%2A5%2B1=16\"\r
\n" ); document.write( "\n" ); document.write( "now find \"k\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"k=+%28a+%2B3%29%2F%28a+-1%29\"..........(1)
\n" ); document.write( "\"k=+8%2F4\"
\n" ); document.write( "\"k=+2\"\r
\n" ); document.write( "\n" ); document.write( "so, the fourth term is \"2%2A16=32\"\r
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