document.write( "Question 970169: What are the next two numbers in this series 1,8,27,58
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Algebra.Com's Answer #592825 by MathLover1(20850)\"\" \"About 
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\"1\",\"8\",\"27\",\"58\"\r
\n" ); document.write( "\n" ); document.write( "first find the pattern:\r
\n" ); document.write( "\n" ); document.write( "To find the pattern, I will list the numbers, and find the differences for each pair of numbers. That is, I will subtract the numbers in pairs (the first from the second, the second from the third, and so on), like this:\r
\n" ); document.write( "\n" ); document.write( "\"1\".........\"8\"..........\"27\"..........\"58\".....\r
\n" ); document.write( "\n" ); document.write( ".....\"7\".........\"19\".........\"31\".... the \"first differences\", are not all the same value, I'll continue subtracting:
\n" ); document.write( "..........\"12\".........\"12\"....=> the second differences are the same, so the polynomial for this sequence of values is a quadratic
\n" ); document.write( "Since the formula for the terms is a quadratic, then I know that it is of the form:\r
\n" ); document.write( "\n" ); document.write( " \"an%5E2+%2B+bn+%2B+c+\" for some numbers \"a\", \"b\", and \"c\"\r
\n" ); document.write( "\n" ); document.write( "Now I have to find those numbers by plugging in some of the values from the sequence, and then solving the resulting system of equations. \r
\n" ); document.write( "\n" ); document.write( "if \"n=1\" first term is \"1\"\r
\n" ); document.write( "\n" ); document.write( "\"a%2A1%5E2+%2B+b%2A1+%2B+c=1+\"
\n" ); document.write( "\"a+%2B+b+%2B+c=1\" ..........eq.1\r
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\n" ); document.write( "\n" ); document.write( "if \"n=2\" second term is \"8\"\r
\n" ); document.write( "\n" ); document.write( "\"a%2A2%5E2+%2B+b%2A2+%2B+c=8+\"
\n" ); document.write( "\"4a+%2B+2b+%2B+c=8\" ..........eq.2\r
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\n" ); document.write( "\n" ); document.write( "if \"n=3\" third term is \"27\"\r
\n" ); document.write( "\n" ); document.write( "\"a%2A3%5E2+%2B+b%2A3+%2B+c=27\"
\n" ); document.write( "\"9a+%2B+3b+%2B+c=27\" ..........eq.3\r
\n" ); document.write( "\n" ); document.write( "start with\r
\n" ); document.write( "\n" ); document.write( "\"4a+%2B+2b+%2B+c=8\" ..........eq.2
\n" ); document.write( "\"a+%2B+b+%2B+c=1\" ..........eq.1
\n" ); document.write( "--------------------------------subtract
\n" ); document.write( "\"3a+%2B+b=7\" --------solve for \"b\"
\n" ); document.write( "\"b=7-3a\".........................(1)\r
\n" ); document.write( "\n" ); document.write( "now use
\n" ); document.write( "\"9a+%2B+3b+%2B+c=27\" ..........eq.3
\n" ); document.write( "\"4a+%2B+2b+%2B+c=8\" ..........eq.2
\n" ); document.write( "--------------------------------subtract
\n" ); document.write( "\"5a%2Bb=19\"--------solve for \"b\"\r
\n" ); document.write( "\n" ); document.write( "\"b=19-5a\".........................(2)\r
\n" ); document.write( "\n" ); document.write( "use (1) and (2) to find \"a\"\r
\n" ); document.write( "\n" ); document.write( "\"7-3a=19-5a\"\r
\n" ); document.write( "\n" ); document.write( "\"5a-3a=19-7\"\r
\n" ); document.write( "\n" ); document.write( "\"2a=12\"\r
\n" ); document.write( "\n" ); document.write( "\"highlight%28a=6%29\"\r
\n" ); document.write( "\n" ); document.write( "now find \"b\"\r
\n" ); document.write( "\n" ); document.write( "\"b=7-3a\".........................(1)
\n" ); document.write( "\"b=7-3%2A6\"
\n" ); document.write( "\"b=7-18\"
\n" ); document.write( "\"highlight%28b=-11%29\"\r
\n" ); document.write( "\n" ); document.write( "go to eq.1 substitute \"a\" and \"b\" , and find \"c\"\r
\n" ); document.write( "\n" ); document.write( "\"a+%2B+b+%2B+c=1\" ..........eq.1
\n" ); document.write( "\"6+-11+%2B+c=1+\"
\n" ); document.write( " \"-5+%2B+c=1+\"
\n" ); document.write( "\"c=1%2B5\"
\n" ); document.write( "\"highlight%28c=6%29\"\r
\n" ); document.write( "\n" ); document.write( "so, your polynomial,or nth term formula is:\r
\n" ); document.write( "\n" ); document.write( "\"a%5Bn%5D+=+6n%5E2-11n%2B6\" .......(for all terms given)\r
\n" ); document.write( "\n" ); document.write( "now use formula to find the next two numbers in this series:\r
\n" ); document.write( "\n" ); document.write( "\"a%5B5%5D+=+6%2A5%5E2-11%2A5%2B6\"\r
\n" ); document.write( "\n" ); document.write( "\"a%5B5%5D+=+150-55%2B6\" \r
\n" ); document.write( "\n" ); document.write( "\"a%5B5%5D+=+101\" \r
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\n" ); document.write( "\n" ); document.write( "\"a%5B6%5D+=+6%2A6%5E2-11%2A6%2B6\"\r
\n" ); document.write( "\n" ); document.write( "\"a%5B6%5D+=+216-66%2B6\" \r
\n" ); document.write( "\n" ); document.write( "\"a%5B6%5D+=+156\" \r
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\n" ); document.write( "\n" ); document.write( "so, with these terms, your sequence is: \"1\",\"8\",\"27\",\"58\",\"101\",\"156\" \r
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