document.write( "Question 1101665: the 15th term in an arithmetic sequence is 129 and the sum of the first fifteen terms is 1095. find the sum if the first ten terms. \n" ); document.write( "
Algebra.Com's Answer #716261 by josgarithmetic(39620)\"\" \"About 
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A, the first term
\n" ); document.write( "The 15th term is \"A%2B14d=129\".
\n" ); document.write( "Sum of first 15 terms is \"%2815%2F2%29%282A%2B14d%29=1095\".
\n" ); document.write( "Two linear equations in A and d.\r
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\n" ); document.write( "\n" ); document.write( "A simplified system of equations: \"system%28A%2B14d=129%2CA%2B7d=73%29\".\r
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\n" ); document.write( "\n" ); document.write( "\"system%28d=8%2CA=17%29\"\r
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\n" ); document.write( "\n" ); document.write( "Sum of first ten terms? \"%2810%2F2%29%2817%2B%2817%2B%2810-1%29%2A8%29%29\"
\n" ); document.write( "Simplify and compute.
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