# I'm confused by equations and the finite differences between the results

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• Aug 11th 2011, 02:17 AM
ribbie
I'm confused by equations and the finite differences between the results
If I have an equation such as 2n2 n 1 then the results of the equation will always be positive. Yet, if I write the results for the equation

1 4 11 22
and then take the finite differences, I discover that the number that precedes 1 in the series is 0, and before that there are negatives, which is impossible when considering the function.
what does this mean?
• Aug 11th 2011, 02:23 AM
Siron
Re: I'm confused by equations and the finite differences between the results
Quote:

Originally Posted by ribbie
If I have an equation such as 2n2 n 1

What does this mean? ...
• Aug 11th 2011, 03:07 AM
ribbie
Re: I'm confused by equations and the finite differences between the results
2n squared plus n plus 1 (I copied and pasted from a different program)
• Aug 11th 2011, 04:27 AM
SpringFan25
Re: I'm confused by equations and the finite differences between the results
I suggest you show us your finite differences and then explain carefully why you think these mean the equation can take negative values.
• Aug 11th 2011, 05:13 AM
ribbie
Re: I'm confused by equations and the finite differences between the results
Quote:

Originally Posted by SpringFan25
I suggest you show us your finite differences and then explain carefully why you think these mean the equation can take negative values.

1 4 11 22
3 7 11
4 4
Those are the values for n = 0 to n = 3
working backwards, I get:
-5 0 1 4 11 22
-5 -1 3 7 11
4 4 4 4
• Aug 11th 2011, 05:25 AM
anonimnystefy
Re: I'm confused by equations and the finite differences between the results
hi ribbie

apparently you didn't subtract correctly because 1-0 ain't -1.the number preceding 1 is 2 and not 0.
• Aug 11th 2011, 05:42 AM
ribbie
Re: I'm confused by equations and the finite differences between the results
Quote:

Originally Posted by anonimnystefy
hi ribbie

apparently you didn't subtract correctly because 1-0 ain't -1.the number preceding 1 is 2 and not 0.

Indeed, spotted the mistake.
Thanks to all...