y=(x + ln(2x))^3. Dy/Dx = ???

Morning guys.

Need a bit of help with the above. I know dy/dx of lnx = 1/x but wasn't sure how to handle the bracketedness.

Thanks.

Reply 1

generalebriety

Do you know the chain rule?

Reply 2

zrancis

Just use the chain rule.

If you obviously multiply the whole function by the power and then reduce it by one, all that's left to do is multiply again by the derivative of x + ln(2x)

Reply 3

Joist

Yeah I can use the chain rule I just didn't really realise this was a situation to!

So you get: dy/dx = 3(x+ln(2x))^2, and then differentiate the bracket?

Reply 4

estel

Yes, which again requires you to use the chain rule.

Reply 5

Joist

Right thanks. So do I then multiply that answer by the first derivitive? (The bracket one)? That's what the mark scheme says and I didn't really understand why...

Reply 6

BlackJackson

I'm 6 years late.. but its because dy/dx = dy/du * du/dx :smile:

Related discussions

Latest

Trending

Articles for you

$What is LaTeX?$

What is LaTeX?

Try out the app

Continue on web