document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=788956>Question 788956</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Fill in the blank to complete this equation:<BR>\n" );
document.write( "1+2+3+...+(n-1)+n+n+(n-1)+...+3+2+1=___________\r<BR>\n" );
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document.write( "I know your suppose to square the (n-1), but I just don't know where to even start. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #478696 by </B><A HREF=/tutors/aboutme.mpl?userid=mananth><B>mananth(16946)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=mananth><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=mananth><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=478696\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> (1+2+3+...+(n-1)+n)+(n+(n-1)+...+3+2+1)=___________<BR>\n" );
document.write( "It consists of 2 same sequences \r<BR>\n" );
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document.write( "Sum of n terms<BR>\n" );
document.write( "Sn = n/2(2a+(n-1)d) <BR>\n" );
document.write( "a=1<BR>\n" );
document.write( "d=1<BR>\n" );
document.write( "n=n\r<BR>\n" );
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document.write( "sn = n/2(2+(n-1)1))\r<BR>\n" );
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document.write( "Sn = n(n+1)/2\r<BR>\n" );
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document.write( "2 Sn = n(n+1)\r<BR>\n" );
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document.write( "n(n+1) </SPAN>\n" );
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