document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=812881>Question 812881</A>: <I><SPAN STYLE=\"word-break: break-all;\"> So I understand how summation and series sequences work but I came across a homework problem that stumped me. I can generally write a sum in summation notation really quickly but I need help with the following.\r<BR>\n" );
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document.write( "Write each sum in summation notation: 1-2+3-4+...+(-50)\r<BR>\n" );
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document.write( "I get that x=1 goes under the sigma notation and 50 goes above it but I am not able to figure out what the formula is. If you could help me I would greatly appreciate it. Thank You </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #489383 by </B><A HREF=/tutors/aboutme.mpl?userid=htmentor><B>htmentor(1343)</B></A><img src=\"/images/stars/stars-12.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=htmentor><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=htmentor><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=489383\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> This series consists of consecutive integers, but the sign alternates.  <BR>\n" );
document.write( "-1 raised to an even power is +1 and -1 raised to an odd power is -1.  So the following summation notation will reproduce the given series:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=sum%28+%28-1%29%5E%28n%2B1%29+%2A+n%2C+n=1%2C+50%29 ALIGN=MIDDLE  ALT=\"sum%28+%28-1%29%5E%28n%2B1%29+%2A+n%2C+n=1%2C+50%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Check:<BR>\n" );
document.write( "The 1st term is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28-1%29%5E2%2A1+=+1 ALIGN=MIDDLE  ALT=\"%28-1%29%5E2%2A1+=+1\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "The 2nd term is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28-1%29%5E3%2A2+=+-2 ALIGN=MIDDLE  ALT=\"%28-1%29%5E3%2A2+=+-2\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "and so on... </SPAN>\n" );
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