# Implicit Differentiation

1. Dec 12, 2005

Assume that y is a function of x . Find y' = dy/dx for (x^3+y^3)^20

when i solved this i got y'= (20(x^3+y^3)^19 * 3x^2)/(-3y^2)

is this correct or am i missing something?

2. Dec 12, 2005

### TD

It's not entirely right, remember that y(x) is an unknown function of x!

$$\begin{gathered} y = \left( {x^3 + y^3 } \right)^{20} \hfill \\ y' = 20\left( {x^3 + y^3 } \right)^{19} \cdot \left( {x^3 + y^3 } \right)^\prime = 20\left( {x^3 + y^3 } \right)^{19} \cdot \left( {3x^2 + 3y^2 \cdot y'} \right) \hfill \\ \end{gathered}$$

Now you can solve for y'.

3. Dec 12, 2005

thanks a lot man. the grader only took off 3 pts for that prob and didnt say anything else, so i didnt know what i did wrong.

THANKS A LOT, you just saved me from making several mistakes on my final exam tommorow :D

4. Dec 13, 2005

Good luck!