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I'm not absolutely sure on how I can deal with this problem with this problem:

Find $ \dfrac{dy}{dx} $ if $ y = 2u^2 - 3u $ and $ u = 4x - 1 $

I am trying to use the chain rule on it.. $$ \dfrac{dy}{dx} = \dfrac{dy}{du} \dfrac{du}{dx} $$

My work so far: $$ \dfrac{d}{du}(2u^2-3u) * \dfrac{d}{dx}(4x-1) = (4u-3)(4) $$

However I am not absolutely sure I am doing it right.. and I don't have the answer in my book.

Thanks for help, it's appreciated !

EDIT: typos.

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    Note that $\frac{dy}{dx}$ should be given in terms of $x$ and not in terms of $u$. If only there was some way of seeing $u$ as a function of $x$......2012-03-11

3 Answers 3