document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1101405>Question 1101405</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In the sequence -12, -7, -2, 3, 8, 13,...determine the 90th term and the sum of the first 80 terms. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #715980 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=715980\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  In the sequence -12, -7, -2, 3, 8, 13,...determine the 90th term and the sum of the first 80 terms. <BR>\n" );
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document.write( "Arithmetic sequence with d = -7-(-12) = 5 and a(1) = -12<BR>\n" );
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document.write( "a(90) = -12 + (89)5 = 433<BR>\n" );
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document.write( "Sum of 1st 80::\r<BR>\n" );
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document.write( "S(80) = (80/2) * (-12+a(80))<BR>\n" );
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document.write( "But, a(80) = -12 + 79*5 = 383<BR>\n" );
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document.write( "So, S(80) = 40*(-12+383) = 14840<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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