document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=302042>Question 302042</A>: <I><SPAN STYLE=\"word-break: break-all;\"> What is the equation of the problem when the number sequence is: 1, 3, 6, 10? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #216649 by </B><A HREF=/tutors/aboutme.mpl?userid=scott8148><B>scott8148(6628)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=scott8148><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=scott8148><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=216649\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> the 2nd level differences are constant (differences of differences), so this is a second order (squared) relation\r<BR>\n" );
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document.write( "a = xn^2 + yn + z\r<BR>\n" );
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document.write( "A) substituting for n=1 ___ 1 = x + y + z\r<BR>\n" );
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document.write( "B) substituting for n=2 ___ 3 = 4x + 2y + z\r<BR>\n" );
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document.write( "C) substituting for n=3 ___ 6 = 9x + 3y + z\r<BR>\n" );
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document.write( "subtracting A) from B) ___ 2 = 3x + y ___ 2 - 3x = y\r<BR>\n" );
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document.write( "subtracting A) from C) ___ 5 = 8x + 2y\r<BR>\n" );
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document.write( "substituting ___ 5 = 8x + 2(2 - 3x) ___ 5 = 8x + 4 - 6x ___ 1 = 2x ___ 1/2 = x\r<BR>\n" );
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document.write( "substituting ___ 2 - 3(1/2) = y ___ 1/2 = y\r<BR>\n" );
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document.write( "substituting ___ 1 = (1/2) + (1/2) + z ___ 0 = z\r<BR>\n" );
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document.write( "the equation is ___ a = (1/2)(n^2 + n) </SPAN>\n" );
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