document.write( "Question 805263: Find the explicit forumla for th following sequence:
\n" ); document.write( "a5= -17 and a28= 374 \n" ); document.write( "

Algebra.Com's Answer #485150 by waynest(281) $\"\"$ $\"About$

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-17 = a + (5-1)d 374 = a + (28 - 1)d
\n" ); document.write( "-17 = a + 4d 374 = a + 27d\r
\n" ); document.write( "\n" ); document.write( "subtract equation 1 from equation 2\r
\n" ); document.write( "\n" ); document.write( " 374 = a + 27d
\n" ); document.write( " -(-17 = a + 4d)
\n" ); document.write( "391 = 23d
\n" ); document.write( "391/23 23d/23
\n" ); document.write( "17 = d\r
\n" ); document.write( "\n" ); document.write( "substitute 17 for d in equation 1
\n" ); document.write( "-17 = a + (5 - 1 )17
\n" ); document.write( "-17 = a + 68
\n" ); document.write( "-17 - 68 = a + 68 - 68
\n" ); document.write( "-85 = a\r
\n" ); document.write( "\n" ); document.write( "substitute both into equation 1 to get the explicit formula
\n" ); document.write( "t(n) = -85 + (n - 1)17
\n" ); document.write( "t(n) = -85 + 17n - 17
\n" ); document.write( "t(n) = 17n - 102\r
\n" ); document.write( "\n" ); document.write( "check:
\n" ); document.write( "t(5) = 17(5) - 102
\n" ); document.write( "t(5) = 86 - 102
\n" ); document.write( "t(5) = -17\r
\n" ); document.write( "\n" ); document.write( "t(28) = 17(28) - 102
\n" ); document.write( "t(28) = 476 - 102
\n" ); document.write( "t(28) = 374 \n" ); document.write( "

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