Derivitive with ln - don't understand

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In summary, the problem is to differentiate y = ln(2x^2 - 2) / x^2 - 1. The solution is y' = -ln(2x^2 - 2)(2x)(x^2 - 1)^-2 + 4x / 2x^2 - 2 (x^2 - 1)^-1. The part that may be confusing is derived using the chain rule. The derivative of ln x is 1/x, so the derivative of ln(2x^2 - 2) would be 1/(2x^2 - 2) * 4x, which simplifies to 4x / 2x^2
  • #1
zeion
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Homework Statement



Differentiate the following:
y = ln(2x^2 - 2) / x^2 - 1



The Attempt at a Solution



The answer is y' = -ln(2x^2 - 2)(2x)(x^2 - 1)^-2 + 4x / 2x^2 - 2 (x^2 - 1)^-1

I understand all of it except 4x / 2x^2 - 2, how does ln(2x^2 - 2) derive into 4x / 2x^2 - 2?
 
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  • #2
[tex]\frac{d}{dx}(ln(f(x))=\frac{f'(x)}{f(x)}[/tex]
 
  • #3
Oh okay, thanks, never seen that one before.
 
  • #4
zeion said:
Oh okay, thanks, never seen that one before.
If you look closely, you'll notice that's just the chain rule...
 
  • #5
Really? How?
 
  • #6
To see how it is the chain rule, think about what the derivative of ln x is.
 

What is a derivative with ln?

A derivative with ln is a mathematical concept that calculates the rate of change of a function that contains a natural logarithm (ln). It is a measure of how much the output of the function changes when the input changes.

How do you find the derivative with ln?

To find the derivative with ln, you can use the chain rule, which states that the derivative of a function within another function is equal to the derivative of the outer function multiplied by the derivative of the inner function. In the case of a function with ln, the derivative of the ln function is equal to 1/x, where x is the input of the function.

Why is it important to understand derivatives with ln?

Understanding derivatives with ln is important in many areas of science, particularly in physics and engineering. It allows us to model and predict the behavior of natural phenomena and make accurate calculations and predictions in various scientific fields.

What are some common mistakes when dealing with derivatives with ln?

One common mistake when dealing with derivatives with ln is forgetting to apply the chain rule, leading to incorrect calculations. Another mistake is not simplifying the expression after taking the derivative, which can make it more difficult to understand and work with.

Can you provide an example of a derivative with ln?

Yes, an example of a derivative with ln is finding the derivative of the function f(x) = ln(3x). The chain rule states that the derivative of ln(3x) is equal to 1/3x multiplied by the derivative of 3x, which is 3. Therefore, the derivative of f(x) is 1/x.

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