document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1010826>Question 1010826</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find the sum of the first 70 terms of the arithmetic sequence: 22,19,16,13<BR>\n" );
document.write( "Find the exact sum of the infinite geometric sequence a (1/2), (-1/4),(1/8) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #626333 by </B><A HREF=/tutors/aboutme.mpl?userid=fractalier><B>fractalier(6550)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=fractalier><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=fractalier><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=626333\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Couple of ways to do this...let me show you one way...<BR>\n" );
document.write( "Let us find the 70th term, by an = a1 + (n-1)d...<BR>\n" );
document.write( "a70 = a1 + 69(-3) = 22 - 207 = -185<BR>\n" );
document.write( "Then Sn = (n/2)(a1 + an) = (70/2)(22 - 207) = 35(-185) = -6475<BR>\n" );
document.write( "For the second one, it's a bit easier...we use<BR>\n" );
document.write( "Sn = a1 / (1 - r) = (1/2) / (1 - (-1/2)) = (1/2) / (3/2) = 1/3 </SPAN>\n" );
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