Chain rule with second derivative

In summary, the conversation is about finding the second derivative of xe^x using the chain rule and product rule. The formula for the nth derivative is also mentioned.
  • #1
beetle2
111
0

Homework Statement



I trying to find the second derivative of [itex]xe^x[/itex]

Homework Equations



chain rule

The Attempt at a Solution



Two find the first derivative I use the chain rule.

[itex]f'(y)g(y)+f(y)g'(y)[/itex]

so I get

[itex]e^x+xe^x[/itex]

is the second derivative

[itex]e^x+f'(y)g(y)+f(y)g'(y)[/itex]

= [itex]e^x+e^x+xe^x[/itex]
= [itex]2e^x+xe^x[/itex]

regards
 
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  • #2
That should be correct, also, you used the product rule, not the chain rule.
 
  • #3
It can be shown that, for any positive integer n, with [itex]f^{(n)}(x)[/itex] indicating the nth derivative, that
[tex](fg)^{(n)}(x)= \sum_{i=0}^n \begin{pmatrix}n \\ i\end{pmatrix}f^{(i)}(x)g^{(n- i)}(x)[/tex]

And, as rock.freak667 said, that is the product rule.
 
  • #4
thanks guys
 

Related to Chain rule with second derivative

1. What is the chain rule with second derivative?

The chain rule with second derivative is a mathematical rule that helps to find the derivative of a function that is composed of two or more functions. It is used when the function has multiple layers or levels of nested functions, and it involves taking the derivative of the outer function, multiplied by the derivative of the inner function.

2. How is the chain rule with second derivative used?

The chain rule with second derivative is used in calculus to find the rate of change of a function that is composed of multiple nested functions. It is particularly useful in solving problems involving optimization, where the goal is to find the maximum or minimum value of a function.

3. Can you provide an example of using the chain rule with second derivative?

For example, if we have a function f(x) = sin(x^2), we can use the chain rule with second derivative to find the derivative of f(x) with respect to x. First, we take the derivative of the outer function, which is cos(x^2). Then, we multiply it by the derivative of the inner function, which is 2x. This gives us the derivative of f(x) = 2x cos(x^2).

4. What is the benefit of using the chain rule with second derivative?

The chain rule with second derivative allows us to find the derivative of a composite function without having to expand and simplify the function. This can save time and effort, particularly when the function is complex and has multiple layers of nested functions.

5. Are there any limitations or special cases for using the chain rule with second derivative?

Yes, the chain rule with second derivative can only be applied when the inner and outer functions are both differentiable. It also does not work for functions that are not continuous. Additionally, if the function has more than two nested functions, the chain rule with second derivative may need to be applied multiple times to find the derivative.

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