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# differentiation help watch

1. hey
how do you differentiate y= 3ln(x^2+1)
I think I need to use the product rule but Im not sure how.. :/
2. (Original post by Kiimii)
hey
how do you differentiate y= 3ln(x^2+1)
I think I need to use the product rule but Im not sure how.. :/
Let y = x^2 +1

So differentiate 3 ln y which gives 3/y.

Then differentiate y with respect to x i.e. differentiate x^2 +1 which gives 2x

Then multiply together to give the answer: 6x/(x^2 +1)

This is the Chain Rule in operation not the product rule.
3. (Original post by Kiimii)
hey
how do you differentiate y= 3ln(x^2+1)
I think I need to use the product rule but Im not sure how.. :/
You don't need to use the product rule.

There's a formula for differentiating logarithmic functions.
It's

The guy above answer is correct so just apply this formula to future questions. But this is a short cut method, what he did was the long way.
4. (Original post by pvaz6965)
Let y = x^2 +1

So differentiate 3 ln y which gives 3/y.

Then differentiate y with respect to x i.e. differentiate x^2 +1 which gives 2x

Then multiply together to give the answer: 6x/(x^2 +1)

This is the Chain Rule in operation not the product rule.
oh ok thank you!
5. (Original post by ServantOfMorgoth)
You don't need to use the product rule.

There's a formula for differentiating logarithmic functions.
It's

The guy above answer is correct so just apply this formula to future questions. But this is a short cut method, what he did was the long way.
thanks!!

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