# Thread: Derivatives

1. ## Derivatives

I need to show that in:

x^3 + y^3 = 6xy

the 2nd derivative is:

Dn^2 = 16xy (2x - y^2) ^-3

how would i solve this?

2. Originally Posted by mandn
I need to show that in:

x^3 + y^3 = 6xy

the 2nd derivative is:

Dn^2 = 16xy (2x - y^2) ^-3

how would i solve this?
Differentiate implicity

the first derivatiev would be $\displaystyle 3x^2+3y^2\frac{dy}{dx}=6x\frac{dy}{dx}+6y$ now solve for $\displaystyle \frac{dy}{dx}$ and then do the same again

3. ok lets try that

4. ok i got that part but what do u do after this step ?

5. Originally Posted by mandn
ok i got that part but what do u do after this step ?
After what step? if you are talking abou the step I showed you you should take the derivative again and solve for $\displaystyle \frac{dy^2}{d^2x}$

and remember you will get a couple $\displaystyle \frac{dy}{dx}$

you will have to sub these for your solved first derivative

6. ok thanks

7. Originally Posted by mandn
ok thanks
If you have any specific problems post them and we will do our best to walk you through them

8. right i will. but need to try solving it first.

9. k good luck