document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=584796>Question 584796</A>: <I><SPAN STYLE=\"word-break: break-all;\"> find the recursive formula of 1,5,12,22,... </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #373087 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=373087\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> 1st difference ___ 4, 7, 10\r<BR>\n" );
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document.write( "2nd difference ___ 3, 3 ___ so formula is 2nd order (squared)\r<BR>\n" );
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document.write( "an^2 + bn + c = Tn\r<BR>\n" );
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document.write( "a(1^2) + b(1) + c = 1 ___ a + b + c = 1 ... (X)\r<BR>\n" );
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document.write( "a(2^2) + b(2) + c = 5 ___ 4a + 2b + c = 5 ... (Y)\r<BR>\n" );
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document.write( "a(3^2) + b(3) + c = 12 ___ 9a + 3b + c = 12 ... (Z)\r<BR>\n" );
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document.write( "subtracting X from Y ___ 3a + b = 4 ... (V)\r<BR>\n" );
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document.write( "subtracting X from z ___ 8a + 2b = 11 ... (W)\r<BR>\n" );
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document.write( "subtracting 2V from W ___ 2a = 3 ___ a = 3/2\r<BR>\n" );
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document.write( "b = -1/2 ___ c = 0\r<BR>\n" );
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document.write( "Tn = (3n^2 - n) / 2 </SPAN>\n" );
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