document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=869683>Question 869683</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Prove that the sum of AP is sn equals(2a+(n-1)d) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #524323 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><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=524323\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> S(n) = ....... a + (a+d) + (a+2d)+......+(a+(n-1)d)<BR>\n" );
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document.write( "S(n) = (a+(n-1)d) + (a+(n-2)d) + (a+(n-3)d)+....+ a<BR>\n" );
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document.write( "Both lines are the sum of n terms of the same AP.<BR>\n" );
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document.write( "Add the 2 lines to get::<BR>\n" );
document.write( "2*S(n) = (2a+(n-1)d) + (2a+(n-1)d)+....+(2a+(n-1)d)<BR>\n" );
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document.write( "2*S(n) = n(2a+(n-1)d)<BR>\n" );
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document.write( "Then S(n) = (n/2)(2a+(n-1)d) = (n/2)(a + [a+(n-1)d])<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
document.write( "===================== </SPAN>\n" );
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