document.write( "Question 1102896: How do you find the polynomial whose graph goes through these points? \r
\n" ); document.write( "\n" ); document.write( "(2,10), (-1,-4), (0,2), and (1,-2).\r
\n" ); document.write( "\n" ); document.write( "Thanks
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Algebra.Com's Answer #717613 by Fombitz(32388)\"\" \"About 
You can put this solution on YOUR website!
You can use EXCEL to do a curve fit.
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\n" ); document.write( "You can use linear algebra to solve a system of equations using a general form of the polynomial.
\n" ); document.write( "\"y=Ax%5E3%2BBx%5E2%2BCx%2BD\"
\n" ); document.write( "So then,
\n" ); document.write( "(2,10):
\n" ); document.write( "\"10=A%282%29%5E3%2BB%282%29%5E2%2BC%282%29%2BD\"
\n" ); document.write( "1.\"8A%2B4B%2B2C%2BD=10\"
\n" ); document.write( "(-1,-4):
\n" ); document.write( "\"-4=A%28-1%29%5E3%2BB%28-1%29%5E2%2BC%28-1%29%2BD\"
\n" ); document.write( "2.\"-A%2BB-C%2BD=-4\"
\n" ); document.write( "(0,2):
\n" ); document.write( "\"2=A%280%29%5E3%2BB%280%29%5E2%2BC%280%29%2BD\"
\n" ); document.write( "3.\"D=2\"
\n" ); document.write( "(1,-2):
\n" ); document.write( "\"-2=A%281%29%5E3%2BB%281%29%5E2%2BC%281%29%2BD\"
\n" ); document.write( "4.\"A%2BB%2BC%2BD=-2\"
\n" ); document.write( "Then substitute eq. 3 into the others,
\n" ); document.write( "\"8A%2B4B%2B2C%2B2=10\"
\n" ); document.write( "\"8A%2B4B%2B2C=8\"
\n" ); document.write( "5.\"4A%2B2B%2BC=4\"
\n" ); document.write( "and
\n" ); document.write( "\"-A%2BB-C%2B2=-4\"
\n" ); document.write( "6.\"-A%2BB-C=-6\"
\n" ); document.write( "and
\n" ); document.write( "\"A%2BB%2BC%2B2=-2\"
\n" ); document.write( "7.\"A%2BB%2BC=-4\"
\n" ); document.write( "Continuing, add eq. 5 and eq. 7 to eq. 6 to eliminate C.
\n" ); document.write( "\"4A%2B2B%2BC-A%2BB-C=4-6\"
\n" ); document.write( "8.\"3A%2B3B=-2\"
\n" ); document.write( "and
\n" ); document.write( "\"A%2BB%2BC-A%2BB-C=-4-6\"
\n" ); document.write( "\"2B=-10\"
\n" ); document.write( "9.\"B=-5\"
\n" ); document.write( "So then working backwards,
\n" ); document.write( "from eq. 8,
\n" ); document.write( "\"3A%2B3%28-5%29=-2\"
\n" ); document.write( "\"3A=-2%2B15\"
\n" ); document.write( "\"A=13%2F3\"
\n" ); document.write( "and from eq. 7,
\n" ); document.write( "\"13%2F3-5%2BC=-4\"
\n" ); document.write( "\"13%2F3-15%2F3%2BC=-12%2F3\"
\n" ); document.write( "\"C=-12%2F3%2B2%2F3\"
\n" ); document.write( "\"C=-10%2F3\"
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\n" ); document.write( "\"y=%2813%2F3%29x%5E3-5x%5E2-%2810%2F3%29x%2B2\"
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\n" ); document.write( "Of course, it matches the EXCEL curve fit.
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