document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=35103>Question 35103</A>: <I><SPAN STYLE=\"word-break: break-all;\"> i really need help on these ones they got me really confused i would appreciate it if i could get some help answering these thank you \r<BR>\n" );
document.write( "\n" );
document.write( "find the sum of the arithmetic sequence having the data given.\r<BR>\n" );
document.write( "\n" );
document.write( "a1 = 5, an = 3, n = 20 \r<BR>\n" );
document.write( "\n" );
document.write( "a1 = 7, d = - 3, n = 20 \r<BR>\n" );
document.write( "\n" );
document.write( "a1 = 81, an = - 13, n = 20 \r<BR>\n" );
document.write( "\n" );
document.write( "a1 = 5, d = 7, n = 120 \r<BR>\n" );
document.write( "\n" );
document.write( "an = 5, d = -2, n = 12 \r<BR>\n" );
document.write( "\n" );
document.write( "In exercises 6-7, find the first term of the arithmetic sequence having the data given. \r<BR>\n" );
document.write( "\n" );
document.write( "an = 48, Sn = 546, n = 26 \r<BR>\n" );
document.write( "\n" );
document.write( "Sn = 781, d = 3, n = 22 \r<BR>\n" );
document.write( "\n" );
document.write( " </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #21330 by </B><A HREF=/tutors/aboutme.mpl?userid=Prithwis><B>Prithwis(166)</B></A><img src=\"/images/stars/stars-09.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Prithwis><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.nriassociation.com/BeliveITorNOT/mittal70millionHouse.jpg valign=middle><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=21330\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Sum S(n) = n/2(a1+an)<BR>\n" );
document.write( "(where n = number of terms; a1 = first term; an = n-th term)<BR>\n" );
document.write( "a1 = 5, an = 3, n = 20 <BR>\n" );
document.write( "=> S(20) = 10(8) = 80; <BR>\n" );
document.write( "Try doing the rest as above;<BR>\n" );
document.write( "If d is known instead of an, Sum S(n) = n[a1 + (n-1)d/2]<BR>\n" );
document.write( "You can use one of the above formula to find the sum of all listed problems;<BR>\n" );
document.write( "For last two problems, you will have to use: an = a1+(n-1)d too. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );