The sum of the first five terms of an arithmetic ...http://yedda.com/questions/Aritihmetic_sequence_Math_8621678601516/?src=rss:qb:qbsThe sum of the first five terms of an arithmetic ...en-usThe sum of the first five terms of an arithmetic ...http://static1.yeddacdn.com/images/Logo132X46_rmt9c1d22d.jpghttp://yedda.com/questions/Aritihmetic_sequence_Math_8621678601516/?src=rss:qb:qbsThe sum of the first five terms of an arithmetic ...The sum of the first five terms of an arithmetic ...http://yedda.com/questions/Aritihmetic_sequence_Math_8621678601516/?src=rss:qb:qbi<p>The sum of the first five terms of an arithmetic sequence is 40 and the sum of the first ten terms is 155. Find an explicit formula for the nth term of the sequence.</p>marewagsmarewagsfemale49questionMon, 25 May 2009 19:44:45 GMThttp://yedda.com/questions/Aritihmetic_sequence_Math_8621678601516/?src=rss:qb:qbiRE: The sum of the first five terms of an arithmetic ...http://yedda.com/questions/Aritihmetic_sequence_Math_8621678601516/------_5_40_a1_a5_2_2a1_4d_5a1_10d_186630718781125?src=rss:qb:qbi<p>Hi, ------ S(5)= 40 = (a1+a5)*5/2= (2a1+4d)5a1+10d ---- 8=a1+2d ----- S(10)= 155 = (a1+a10)*10/2= (a1+a1+9d)*5 = 10a1+45d -------- 31=2a1+9d From the 1st equation: a1=8-2d install in the 2nd equation: 31=2(8-2d)+9d ----- 31=16-4d+9d ---- 15=5d d=3 and a1=2 ------- a9=a1+8d ------ a9=2+3*8=26 -------- Best regards, </p>OronDOronDmale110answer4.0Tue, 26 May 2009 05:58:37 GMThttp://yedda.com/questions/Aritihmetic_sequence_Math_8621678601516/------_5_40_a1_a5_2_2a1_4d_5a1_10d_186630718781125?src=rss:qb:qbiRE: The sum of the first five terms of an arithmetic ...http://yedda.com/questions/Aritihmetic_sequence_Math_8621678601516/d_2d_3d_4d_5d_6d_7d_8d_9d_5a_10d_40_862087137133275?src=rss:qb:qbi<p>a + (a + d) + (a + 2d) + (a + 3d) + (a + 4d)</p> <p>(a+5d) + (a+6d) + (a+7d) + (a+8d) + (a+9d)</p> <p>5a + 10d = 40                                         (a)</p> <p>10a + 45d = 155                                      (b)</p> <p>10a + 20d = 80                                      2 x(a)</p> <p>25d = 75                                           (b) - 2 x(a)</p> <p>d = 3</p> <p>a + 2d = 8 = a + 6                           from (a)/5</p> <p>a = 2</p> <p>Sequence is 2, 5, 8, etc.</p> <p>nth term is a + (n -1)d = 2 + 3(n -1) = 3n -1</p> <p>Every term is a multiple of three reduced by 1</p> <p>Regards - Ian</p> <p> </p> <p> </p> <p> </p> <p><br/> </p>IanIanmale61answer3.0Sat, 30 May 2009 22:28:37 GMThttp://yedda.com/questions/Aritihmetic_sequence_Math_8621678601516/d_2d_3d_4d_5d_6d_7d_8d_9d_5a_10d_40_862087137133275?src=rss:qb:qbi