# Prove that ord(f) = nWatch

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#1
Need a quick help as to where to start with this question, literally befuddled;
'Prove that ord(f) = n if and only if f(0) = ··· = f^(n−1)(0) = 0.
and
f^(n)(0) ̸= 0, where f^(k) denotes the k-th derivative of f. '

0
5 years ago
#2
(Original post by H.Maleki)
..
What does "ord(f)" mean / how is it defined?
0
#3
(Original post by ghostwalker)
What does "ord(f)" mean / how is it defined?
Its for a formal power series if that helps?
0
5 years ago
#4
(Original post by H.Maleki)
Its for a formal power series if that helps?
But what does ord(f) mean?

It's not a notation I've ever seen - how is it defined in your notes or book?
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#5
(Original post by davros)
But what does ord(f) mean?

It's not a notation I've ever seen - how is it defined in your notes or book?
this is all I'm given:

http://imgur.com/u7EmtWg
0
5 years ago
#6
(Original post by H.Maleki)
this is all I'm given:

http://imgur.com/u7EmtWg
If you are unsure of how to start, write down all the definitions and think how they relate. E.g. what does f(0) mean? What about f(0)=0? What about ord(f) =1? It may also help to write f(t) explicitly as in the definition.
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