Math Is Fun Forum

ninjaman

Member

Registered: 2013-10-15

Posts: 61

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:)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: differentiation

Hi;

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

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

ninjaman

Member

Registered: 2013-10-15

Posts: 61

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

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

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.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.