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# Differentiating watch

1. Hi,

I'm doing this question: Attachment 536465536469

I have underlined the one part I don't understand in red.

shouldn't it be multiplied by dy/dx as you are differentiating dy/dz (a derivative of y) with respect to x?

Thanks for any help.
Attached Images

2. (Original post by Sir_Malc)
Hi,

I'm doing this question: Attachment 536465536469

I have underlined the one part I don't understand in red.

shouldn't it be multiplied by dy/dx as you are differentiating dy/dz (a derivative of y) with respect to x?

Thanks for any help.
Chain rule:

3. Thanks for the help.

I cant finish this question off though. I plugged in my answer but cant get rid of the '2-x' part:

Sorry if I'm being dumb.
Attached Images

4. (Original post by Sir_Malc)
Thanks for the help.

I cant finish this question off though. I plugged in my answer but cant get rid of the '2-x' part:

Sorry if I'm being dumb.
You're having problems because you're subsituting in too early which leads to mistakes when dealing with all the exponentials.

You want to write and without any exponentials first.

E.g.

Now try to do the same for .

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