document.write( "Question 1083503: Given the arithmetic series : 12+18+24+....+2880
\n" ); document.write( "Calculate the sum of all the terms of the series tht are not visible by 4 \r
\n" ); document.write( "\n" ); document.write( "6x+12;2x+4;andx-7 are the first three terms of a geometric sequence
\n" ); document.write( "Solve for x\r
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Algebra.Com's Answer #697516 by KMST(5328)\"\" \"About 
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The common difference is 6, and A\all terms are divisible by 6,
\n" ); document.write( "from \"6%2A2=12=4%2A3\" to \"6%2A480=2880=4%2A180%2A6\" .
\n" ); document.write( "First and last terms \"12\" and \"2880\" are divisible by 4.
\n" ); document.write( "However, with a common difference of \"6=3%2A2\" ,
\n" ); document.write( "every other term will be not divisible by 4.
\n" ); document.write( "Those terms from an arithmetic series with common difference \"6%2A2=12\" ,
\n" ); document.write( "from \"a%5B1%5D=6%2A3=18\" to \"a%5Bn%5D=6%2A479=2874\" .
\n" ); document.write( "The difference between first and last term is
\n" ); document.write( "\"a%5Bn%5D-a%5B1%5D=12%28n-1%29=6%2A479-6%2A3=6%28479-3%29=6%2A476=6%2A2%2A238=12%2A238\" .
\n" ); document.write( "So, \"n-1=238\" ---> \"n=239\"
\n" ); document.write( "The sum of those \"n\" terms is
\n" ); document.write( "\"n%28a%5B1%5D%2Ba%5Bn%5D%29%2F2=239%2818%2B2874%29%2F2=239%2A2892%2F2=highlight%28345594%29\"
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\n" ); document.write( "The common ratio of that geometric sequence is
\n" ); document.write( "\"%28x-7%29%2F%282x%2B4%29=%282x%2B4%29%2F%286x%2B12%29\"
\n" ); document.write( "Solving:
\n" ); document.write( "\"%28x-7%29%2F%282x%2B4%29=%282x%2B4%29%2F%286x%2B12%29\"
\n" ); document.write( "\"%28x-7%29%2F%282%28x%2B2%29%29=%282x%2B4%29%2F%286%28x%2B2%29%29\"
\n" ); document.write( "Denominators require \"x%2B2%3C%3E0%29\" <--> \"x%3C%3E-2\"
\n" ); document.write( "Multiplying both sides times \"12%28x%2B2%29\" , we gw=et
\n" ); document.write( "\"6%28x-7%29=2%282x%2B4%29\"
\n" ); document.write( "\"6x-42%29=4x%2B8\"
\n" ); document.write( "\"6x-4x=42%2B8\"
\n" ); document.write( "\"2x=50\"
\n" ); document.write( "\"highlight%28x=25%29\"
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