document.write( "Question 1018384: justify y=x^2 using finite differences? \n" ); document.write( "
Algebra.Com's Answer #634500 by rothauserc(4718)\"\" \"About 
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write out the following sequence
\n" ); document.write( "1 4 9 16 25
\n" ); document.write( "calculate the difference between the terms
\n" ); document.write( " 3 5 7 9
\n" ); document.write( "calculate the difference between the new terms
\n" ); document.write( " 2 2 2
\n" ); document.write( "On the second line, the differences are all the same, the method of finite differences tells us that the polynomial generating this sequence is of order 2
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\n" ); document.write( "the general form is f(x) = ax^2 +bx +c
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\n" ); document.write( "let's look at f(1), f(2), f(3)
\n" ); document.write( "f(1) = a + b + c = 1
\n" ); document.write( "f(2) = 4a + 2b + c = 4
\n" ); document.write( "f(3) = 9a + 3b + c = 9
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\n" ); document.write( "solving for a, b , c we see that a=1, b=0, c=0, therefore
\n" ); document.write( ":
\n" ); document.write( "f(x) = x^2 is our solution
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