document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=819797>Question 819797</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The sum of the first 20 terms of an arithmetic sequence is 840. If the common difference is 4, find<BR>\n" );
document.write( "(a) The first term<BR>\n" );
document.write( "(b) The sum of the first 30 terms </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #493239 by </B><A HREF=/tutors/aboutme.mpl?userid=Ms.+U><B>Ms. U(2)</B></A><img src=\"/images/stars/iconNewId_16x16.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Ms.+U><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=Ms.+U><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=493239\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Formula: S= n/2(2a+(n-1)d) <BR>\n" );
document.write( "where <BR>\n" );
document.write( "s = sum of progression <BR>\n" );
document.write( "n = number of terms <BR>\n" );
document.write( "a = value of first term <BR>\n" );
document.write( "d = difference between 2 terms or the common difference\r<BR>\n" );
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document.write( "(a)<BR>\n" );
document.write( "Given:<BR>\n" );
document.write( "d= 4<BR>\n" );
document.write( "S(sum of the 20 terms)=840<BR>\n" );
document.write( "n= 20 (because there are 20 terms)<BR>\n" );
document.write( "a= ???\r<BR>\n" );
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document.write( "Substitute the given value.<BR>\n" );
document.write( "840 = 20/2[2a+(20-1)4]<BR>\n" );
document.write( "840 = 10[2a+ (19)4]<BR>\n" );
document.write( "840 = 10 (2a + 76)   *Distribute 10 in(2a + 76)*<BR>\n" );
document.write( "840 = 20a + 760  *Transpose 760 to the left side of the equal sign.<BR>\n" );
document.write( "840 - 760 = 20a<BR>\n" );
document.write( "80 = 20a  * Divide both sides by 20.<BR>\n" );
document.write( "80/20 = 20a/20<BR>\n" );
document.write( "a= 4 \r<BR>\n" );
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document.write( "The first term is 4.\r<BR>\n" );
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document.write( "(b)<BR>\n" );
document.write( "a= 4<BR>\n" );
document.write( "d= 4<BR>\n" );
document.write( "n= 30<BR>\n" );
document.write( "S(sum of the 30 terms)=???\r<BR>\n" );
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document.write( "S= 30/2 [2(4)+ (30-1)4]<BR>\n" );
document.write( "S= 15 [8 + (29)4]<BR>\n" );
document.write( "S= 15 [8 + 116]<BR>\n" );
document.write( "S= 15 (124)<BR>\n" );
document.write( "S= 1860\r<BR>\n" );
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document.write( "The sum of the first 30 terms is 1860. </SPAN>\n" );
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