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## Main Question or Discussion Point

How would one expand f+df about x? I'm messing something up in the process and can't seem to resolve it lol

- Thread starter rexregisanimi
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- #1

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How would one expand f+df about x? I'm messing something up in the process and can't seem to resolve it lol

- #2

mfb

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How are they related to x?

There is way too much context missing to answer that.

- #3

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It shouldn't matter; f is a function of x (and other variables)...

- #4

pwsnafu

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You can't Taylor expand around a variable. You expand around a fixed base point. That's why we write the polynomials terms as ##(x-a)^n##, i.e. expand around a.It shouldn't matter; f is a function of x (and other variables)...

- #5

mfb

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It does matter. Letters without any definition are pointless.It shouldn't matter;

It is like asking "what is x+y?" You cannot answer it (apart from "it is x+y") if you have no idea what x and y are.

- #6

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I was either communicating poorly or something. I found my answer.

f+df = f +(df/dx)dx + (d2f/dx2)dx2 + ... [The parenthetical terms are partials but not the differentials.]

My favorite is, "It does matter. Letters without any definition are pointless." And to think I wasted all that time learning Algebra! :/

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