document.write( "Question 144227: select the next number in the series:
\n" ); document.write( "298 209 129 58 -4\r
\n" ); document.write( "\n" ); document.write( "choices are -13, -93, -66, -57 \n" ); document.write( "
Algebra.Com's Answer #104996 by stanbon(75887)\"\" \"About 
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select the next number in the series:
\n" ); document.write( "298 209 129 58 -4\r
\n" ); document.write( "\n" ); document.write( "choices are -13, -93, -66, -57
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\n" ); document.write( "You take the successive differences and get:
\n" ); document.write( "89....80....71...62
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\n" ); document.write( "You take the successive differences again and get:
\n" ); document.write( "9.....9....9
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\n" ); document.write( "This tells you the pattern is quadratic
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\n" ); document.write( "Using the form y = ax^2+bx+c you generate three equations by
\n" ); document.write( "substituting three points from the following:(1,298) (2,209) (3,129) (4,58) (4,-4)
\n" ); document.write( "Doing that will give you three equations in a,b, c.
\n" ); document.write( "Solve the system of equations and determine f(6) to get the
\n" ); document.write( "next number in the sequence.
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\n" ); document.write( "I get -57.
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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