Use the chain rule to find the derivative

In summary, the question is asking for the derivative of the function f(x) = ((x^2+2)^2)/(x+2)^1/2 using the chain rule. The attempt at a solution incorrectly uses only the power rule, missing the fact that it is a quotient and that the quotient rule should be used first. Alternatively, the function can be rewritten as f(x) = (x^2+2)^2(x+2)^{-1/2} and the product rule, along with the chain rule, can be used to find the derivative.
  • #1
Mathysics
37
0

Homework Statement


f(x) = ((x^2+2)^2)/(x+2)^1/2
Use the chain rule to find the derivative

Homework Equations


None


The Attempt at a Solution


((x^2+2)^2)(x+2)^-1/2

PS: Answer in the book is 3x((x^2+2)^1/2)

I have no idea how they get it there, would like some help, thx!
 
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  • #2


Mathysics said:

Homework Statement


f(x) = ((x^2+2)^2)/(x+2)^1/2
Use the chain rule to find the derivative

Homework Equations


None


The Attempt at a Solution


((x^2+2)^2)(x+2)^-1/2

PS: Answer in the book is 3x((x^2+2)^1/2)

I have no idea how they get it there, would like some help, thx!
It looks like you completely missed the fact that this is a quotient (use the quotient rule first). As part of using the quotient rule, you'll need the chain rule.
 
  • #3


Mark44 said:
It looks like you completely missed the fact that this is a quotient (use the quotient rule first). As part of using the quotient rule, you'll need the chain rule.

ohh thx! I will try it again (reserved)
 
  • #4


BTW, questions on derivatives really should go in the Calculus & Beyond section, not the Precalc section.
 
  • #5


Or, since the product rule is (to me anyway) less complicated than the quotient rule, write your function as [itex]f(x) = (x^2+2)^2(x+2)^{-1/2}[/itex] and use the product rule, together with the chain rule.
 

1. What is the chain rule?

The chain rule is a mathematical rule used to find the derivative of a composite function, which is a function that is made up of two or more functions. It states that the derivative of a composite function is equal to the derivative of the outer function multiplied by the derivative of the inner function.

2. When should I use the chain rule?

The chain rule should be used when you have a composite function and need to find its derivative. This usually occurs when you have a function within a function, such as f(g(x)).

3. How do I apply the chain rule?

To apply the chain rule, you first need to identify the outer function and the inner function. Then, you can use the formula: (d/dx)f(g(x)) = f'(g(x)) * g'(x), where f'(g(x)) represents the derivative of the outer function and g'(x) represents the derivative of the inner function.

4. Can you provide an example of using the chain rule to find a derivative?

Sure, let's say we have the function f(x) = sin(3x). To find its derivative, we can first identify the outer function, which is sin(x). Then, we can identify the inner function, which is 3x. Applying the chain rule, we get f'(x) = cos(3x) * 3 = 3cos(3x).

5. What are some common mistakes when using the chain rule?

One common mistake is forgetting to take the derivative of the outer function. Another mistake is mixing up the order of operations and finding the derivative of the outer function before multiplying by the derivative of the inner function. It's important to carefully identify and follow the steps of the chain rule to avoid these mistakes.

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