document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1143233>Question 1143233</A>: <I><SPAN STYLE=\"word-break: break-all;\"> 1.3 For an arithmetic series consisting of 15 terms Sn=2n-n^2\r<BR>\n" );
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document.write( "Determine:\r<BR>\n" );
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document.write( "(a) the first term of the sequence.\r<BR>\n" );
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document.write( "(b) the sum of the last 3 terms \r<BR>\n" );
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document.write( "Please help me please  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #764034 by </B><A HREF=/tutors/aboutme.mpl?userid=greenestamps><B>greenestamps(13200)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=greenestamps><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=greenestamps><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=764034\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <br><BR>\n" );
document.write( "The n-th term is the difference between the sum of the first n terms and the sum of the first (n-1) terms:<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%28n%29+=+%282n-n%5E2%29-%282%28n-1%29-%28n-1%29%5E2%29+=+%282n-n%5E2%29-%282n-2-n%5E2%2B2n-1%29+=+-2n%2B3 ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "So the first term is -2(1)+3 =1 and the common difference is -2.<br><BR>\n" );
document.write( "ANSWERS:<BR>\n" );
document.write( "(a) the first term is 1<BR>\n" );
document.write( "(b) since the sequence is arithmetic, the sum of the last three terms (terms 13, 14, and 15) is 3 times the 14th term:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=3%28-2%2814%29%2B3%29+=+3%28-28%2B3%29+=+3%28-25%29+=+-75 ALIGN=MIDDLE  ALT=\"3%28-2%2814%29%2B3%29+=+3%28-28%2B3%29+=+3%28-25%29+=+-75\"   DISABLED_style= \"max-width:90%; height:auto;\" > </SPAN>\n" );
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