document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=892169>Question 892169</A>: <I><SPAN STYLE=\"word-break: break-all;\"> the second term of an arithmetic sequence is 7, the sum of the first four terms in the arithmetic sequence is 12, find the first term and the common difference<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #540350 by </B><A HREF=/tutors/aboutme.mpl?userid=richwmiller><B>richwmiller(17219)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=richwmiller><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=richwmiller><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=540350\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> S = ½(a + an)n<BR>\n" );
document.write( "S = ½(2a + (n-1)d)n<BR>\n" );
document.write( "an = a + (n - 1)d<BR>\n" );
document.write( "S = ½(a + an)n<BR>\n" );
document.write( "S = ½(2a + (n-1)d)n<BR>\n" );
document.write( "12 = 4a + 6d<BR>\n" );
document.write( "7= a + d<BR>\n" );
document.write( "a=15<BR>\n" );
document.write( "d=-8<BR>\n" );
document.write( "a12 = 15 + 3*(-8)<BR>\n" );
document.write( "a12=15-24=-9<BR>\n" );
document.write( "a12=-9\r<BR>\n" );
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document.write( "S4 = ½(2*15 + (3)*(-8))4<BR>\n" );
document.write( "S4=2*(30-24)<BR>\n" );
document.write( "S4=12\r<BR>\n" );
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document.write( "15,7,-1,-9=22-10=12\r<BR>\n" );
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