Derivatives Adv Calc: Show f'(x) = f'(0)f(x)

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Homework Help Overview

The problem involves a differentiable function f at x=0, with the condition that f'(0) is not equal to zero for all real numbers. The goal is to show that f'(x) = f'(0)f(x) given the functional equation f(a+b) = f(a)f(b).

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the implications of the condition "for all real numbers" in relation to f'(0). There is a suggestion to express f'(x) as a difference quotient. Some participants question the correctness of the problem statement, citing counterexamples. Others express confusion about the limit process involved in calculating the derivative.

Discussion Status

The discussion is ongoing, with participants exploring various interpretations of the problem and raising questions about the definitions and implications of the derivative. Some guidance has been offered regarding the definition of the derivative, but there is no explicit consensus on the problem's formulation or approach.

Contextual Notes

There are indications of confusion regarding the problem statement and its implications, as well as a mention of an upcoming test, which may influence participants' engagement and understanding.

chief12
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Homework Statement


function f is differentiable when x=0,

f'(0) is not equal to zero for all real Numbers

f(a+b) = f(a)f(b)

show f'(x) = f'(0)f(x)

Homework Equations


The Attempt at a Solution



f(x+0) = f(x) = f(x)f(0)
this shows f(0) = 1

then i get stuck..
 
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chief12 said:

Homework Statement


function f is differentiable when x=0,

f'(0) is not equal to zero for all real Numbers

What does "for all real numbers" have to do with f'(0)?

f(a+b) = f(a)f(b)

show f'(x) = f'(x)f(x)

You clearly haven't stated the problem correctly since f(x) = ex is a counterexample.
 
LCKurtz said:
What does "for all real numbers" have to do with f'(0)?



You clearly haven't stated the problem correctly since f(x) = ex is a counterexample.
\for some reason it quoted wrong i guess, it said f'(x) = f'(0)f(x)
 
Write f'(x) as a difference quotient.
 
What happens when you try to calculate f'(x) by taking the limit of the difference quotient?
 
LCKurtz said:
What happens when you try to calculate f'(x) by taking the limit of the difference quotient?

I don't know what that means, please explain... test tomorrow
 
LCKurtz said:
What happens when you try to calculate f'(x) by taking the limit of the difference quotient?

chief12 said:
I don't know what that means, please explain... test tomorrow

Surely the definition of a derivative is in your text:

[tex]f'(x) = \lim_{h\rightarrow 0}\frac{f(x+h)-f(x)}{h}[/tex]
 

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