document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=881938>Question 881938</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Can you please show me how to work this out? I would really be thankful!!\r<BR>\n" );
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document.write( "What is the sum of the arithmetic sequence 3, 9, 15..., if there are 26 terms?\r<BR>\n" );
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document.write( " 1,452\r<BR>\n" );
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document.write( " 1,728\r<BR>\n" );
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document.write( " 2,028\r<BR>\n" );
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document.write( " 2,268<BR>\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 #532618 by </B><A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><B>jim_thompson5910(35256)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=jim_thompson5910><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=532618\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The common difference is 9 - 3 = 6. So d = 6\r<BR>\n" );
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document.write( "First term: a1 = 3\r<BR>\n" );
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document.write( "Sn = n*(a1 + an)/2\r<BR>\n" );
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document.write( "Sn = n*(a1 + a1 + (n-1)*d)/2\r<BR>\n" );
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document.write( "Sn = n*(2*a1 + (n-1)*d)/2\r<BR>\n" );
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document.write( "S26 = 26*(2*a1 + (26-1)*d)/2 ... plug in n = 26\r<BR>\n" );
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document.write( "S26 = 26*(2*3 + (26-1)*d)/2 ... plug in a1 = 3\r<BR>\n" );
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document.write( "S26 = 26*(2*3 + (26-1)*6)/2 ... plug in d = 6\r<BR>\n" );
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document.write( "S26 = <font color=\"red\">2,028</font>\r<BR>\n" );
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document.write( "The sum of the first 26 terms is <font color=\"red\">2,028</font> </SPAN>\n" );
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