Quick question

  • Thread starter Gill
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  • #1
Gill
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i got this question from a friend and its bugging me because i cannot understand it. i just cannot understand what it means... here is it, word for word what i have on the assigned paper

"if f(x) = x^n , "n" is a positive interger, the first derivative of f(x) which is identically zero is "

A) the nth
B) the (n-1)st
C) the (n+2)nd
D) the first
E) the (n+1)st

those are the options...am I to assume that its so easy that its B? i am hesitant to pick B tho because this teacher is known for his tricks and it seemed a little too easy...a little help would be great for my friend and myself
 

Answers and Replies

  • #2
Tide
Science Advisor
Homework Helper
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I suggest trying a few simple example like [itex]x^2[/itex] and so forth - you should see a pattern emerge! :)
 
  • #3
Knavish
116
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Basically, it takes n iterations to get to a constant, and then one more.
 
  • #4
scholzie
75
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Not sure if you got this already, but the question is asking "How many times do you need to differentiate this thing to get 0?"

It's worded in a tricky manner, but essentially, what do you know about differentiating a constant? How many times will you need to differentiate to get a constant? Then, how many times will you have to differentiate that to get 0?

PS - please use more descriptive thread titles. I've noticed a few threads by you with no indication as to what lies within. It makes it very difficult to get help when you need it if people skip over it!
 
  • #5
scorpion
8
0
The answer is n+1 times

The hint lies in the fact
The nth differential of f(X)=x^n gives a constant
And n+1th diffrential i.e of a constant gives us Zero
 
  • #6
borisleprof
36
0
Remember that each time you take de derivative, the exponent reduces by one.
And the derivative of a constant is zero.
Ciao
 

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