document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=940801>Question 940801</A>: <I><SPAN STYLE=\"word-break: break-all;\">  The first three terms of an arithmetic series are 60, 4p and 2p – 6 respectively.<BR>\n" );
document.write( " Show that p = 9\r<BR>\n" );
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document.write( "Find the value of the 20th term of this series.\r<BR>\n" );
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document.write( "Prove that the sum of the first n terms of this series is given by the expression<BR>\n" );
document.write( "12n (6 – n) </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #573425 by </B><A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><B>josgarithmetic(39625)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=josgarithmetic><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=573425\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Difference between successive terms is a constant.\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=4p-60=2p-6-4p ALIGN=MIDDLE  ALT=\"4p-60=2p-6-4p\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=6p-60=-6 ALIGN=MIDDLE  ALT=\"6p-60=-6\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=p-10=-1 ALIGN=MIDDLE  ALT=\"p-10=-1\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%28p=9%29 ALIGN=MIDDLE  ALT=\"highlight%28p=9%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( "The three terms are:  60, 36, 12<BR>\n" );
document.write( "Common difference is <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=-24 ALIGN=MIDDLE  ALT=\"-24\"   DISABLED_style= \"max-width:90%; height:auto;\" >.\r<BR>\n" );
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document.write( "General term,  <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=highlight%2860-%28n-1%2924%29 ALIGN=MIDDLE  ALT=\"highlight%2860-%28n-1%2924%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "n is the index for the term.\r<BR>\n" );
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document.write( "The general term is usually stated as <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=A%5B1%5D%2B%28n-1%29d ALIGN=MIDDLE  ALT=\"A%5B1%5D%2B%28n-1%29d\"   DISABLED_style= \"max-width:90%; height:auto;\" >, but you know from your specific example that d=-24, so subtraction is shown for the general term of your example.  You would evaluate <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=60-%2819%29%2824%29 ALIGN=MIDDLE  ALT=\"60-%2819%29%2824%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >. </SPAN>\n" );
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