# Thread: struggling to find a dirivative

1. ## struggling to find a dirivative

How do i find the dirivative of y=x-1/2x^2.
Thats. y=x - 1 divided by 2x to the power 2.

Any help would be greatful.
Thanks, James.

(where does the math notations everyone seems to use come from? )

2. Split the fraction in two pieces, then use the power rule for derivatives.

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LaTeX stuff can be found here.

3. Originally Posted by james jarvis
How do i find the dirivative of y=x-1/2x^2.
Thats. y=x - 1 divided by 2x to the power 2.

Any help would be greatful.
Thanks, James.

(where does the math notations everyone seems to use come from? )
We use Latex. (I'll go search for the tutorial and then edit my post and paste it here okay?)

$( \frac{x - 1}{2x} )^{2}$

$= (x(2x)^{-1} - 1(2x)^{-1})^{2}$

$= \frac{1}{4} - \frac{1}{2} x^{-1} + \frac{1}{4}x^{-2}$

$\frac{dy}{dx} = 0 + \frac{1}{2} x^{-2} - \frac{1}{2}x^{-3}$

$= \frac{1}{2x^2} - \frac{1}{2x^3}$

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EDIT: Krizalid gave you the link

4. Thanks for reply. Always makes sense when you see it!

5. Originally Posted by james jarvis
Always makes sense when you see it!
You bet!

6. ## How to find derivative

Your question is not clear.

a) Is the 2x under the 1 only or under x as well?

b) Is it (2)(x^2) or is it (2x)^2. That is, is it just the x that is raised to power 2 or the 2x?

Tell me which is which and I will tell you......how

7. Originally Posted by jackddog
Your question is not clear.

a) Is the 2x under the 1 only or under x as well?

b) Is it (2)(x^2) or is it (2x)^2. That is, is it just the x that is raised to power 2 or the 2x?

Tell me which is which and I will tell you......how
Well my approach seems to be correct as he seems happy with it

8. I think you use the Quotient Rule.