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## #1 2014-01-14 11:53:11

ninjaman
Member
Registered: 2013-10-15
Posts: 43

### differentiation

hello
I have a question im stuck with

y = (7x-4) 3/2         (3/2 is supposed to be 3 over 2, I don't know how to do that on here)

I got this,

u = 7x-4

du/dx = 7

y = u 3/2

dy/du = 3/2u -3/2  (the -3/2 is power, supposed to be above right of u)

du/dx * dy/du = 3/2u-3/2 * 7 = 21/2 u -3/2

since u = 7x-4,      21/2 (7x-4) -3/2

im thinking most of it is correct except for the -3/2, the fraction part has me concerned.

thanks

simon:)

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## #2 2014-01-14 15:20:38

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 92,921

### Re: differentiation

Hi;

ninjaman wrote:

dy/du = 3/2u -3/2  (the -3/2 is power, supposed to be above right of u)

You made a mistake in the above step. You did not apply the power rule correctly. Here are the steps for the whole problem.

You can use latex for all your math posting. I use this when I am not doing it by hand,

http://latex.codecogs.com/editor.php

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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## #3 2014-01-15 05:48:06

ninjaman
Member
Registered: 2013-10-15
Posts: 43

### Re: differentiation

thanks a lot, I looked at the bit where you put in a radical(I think that's what its called, the sqrt sign) that threw me.
thanks also for the latex thing, that will help a lot when writing out maths stuff!

all the best
simon

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## #4 2014-01-15 05:58:11

bobbym
From: Bumpkinland
Registered: 2009-04-12
Posts: 92,921

### Re: differentiation

Hi;

It makes perfect latex so everything looks nice and neat.

In mathematics, you don't understand things. You just get used to them.

I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.

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