General expression for the derivative?

In summary, the conversation is about finding the general form for the nth derivative of a function involving logarithms and an arbitrary value for m. The speaker has found a formula for the nth derivative but is still trying to find a general form for the coefficients. However, it is mentioned that the Leibniz rule determines the coefficients and cannot be changed.
  • #1
rsq_a
107
1
I'm trying to find the general form for the nth derivative of
[tex]
f(x) = \frac{1}{x^m \log x}
[/tex]

where m can be anything (set m = 1 for instance). For ease, you can take m to be integral.

It sounds surprisingly simple, but the most I've been able to say is
[tex]
f^{(n)}(x) = (-1)^n x^{-(m+n)} \sum_{k=0}^n a_{k, n} [\log(x)]^{-k}
[/tex]

where the coefficients satisfy
[tex]
a_{k,n} = [m + (n-1)] a_{k, n-1} + (k-1) a_{k-1, n-1}
[/tex]

for 0 < k < n, and with [tex]a_{0, n} = (m + n - 1)!/(m-1)![/tex] and [tex]a_{n,n} = n![/tex]

Unfortunately, I was hoping to get a general form for the coefficients. Does anyone know a trick?
 
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  • #2
There is no trick. The Leibniz rule is responsible for the coefficients and you can't change that.
 

FAQ: General expression for the derivative?

What is the general expression for the derivative?

The general expression for the derivative of a function f(x) is given by f'(x) = lim(h->0) [f(x+h) - f(x)]/h, where h is the change in x. This expression represents the slope of the tangent line to the graph of f(x) at a particular point x.

How is the general expression for the derivative derived?

The general expression for the derivative is derived using the concept of limits. It is based on the definition of the derivative, which is the instantaneous rate of change of a function at a specific point. By taking the limit of the difference quotient as h approaches 0, we can find the exact value of the derivative at that point.

3. Can the general expression for the derivative be used for all types of functions?

Yes, the general expression for the derivative can be used for all types of functions, including polynomial, trigonometric, exponential, and logarithmic functions. However, the process of finding the derivative may differ for each type of function.

4. What is the significance of the general expression for the derivative?

The general expression for the derivative is significant because it allows us to calculate the rate of change of a function at a particular point. This is useful in many applications, such as finding the maximum and minimum values of a function, determining the velocity and acceleration of an object, and solving optimization problems.

5. Are there any alternative expressions for the derivative?

Yes, there are alternative expressions for the derivative, such as the power rule, product rule, quotient rule, and chain rule. These rules provide a shortcut method for finding the derivative of more complex functions. However, they are all derived from the general expression for the derivative.

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