document.write( "Question 999847: the last three terms of an arithmetic sequence with 18 terms are 67, 72,77 . Find the first term and the sum of the series \n" ); document.write( "

Algebra.Com's Answer #617393 by josgarithmetic(39618) $\"\"$ $\"About$

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$\"A%2B%28n-1%29%2A5=77\"$ when n=18, so substitution of this index will give an equation with only A as the unknown, and is solvable.\r
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\n" ); document.write( "\n" ); document.write( " $\"A%2B%2818-1%29%2A5=77\"$
\n" ); document.write( " $\"A=77-17%2A5\"$
\n" ); document.write( " $\"A=77-85\"$
\n" ); document.write( " $\"highlight%28A=-8%29\"$ \n" ); document.write( "

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