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Mathematics 7 Online
OpenStudy (johnnydicamillo):

find y' by implicit differentiation

OpenStudy (johnnydicamillo):

\[2x^3+x^2y-xy^3 = 2\]

OpenStudy (freckles):

you know d(2x^3)/dx=?

OpenStudy (johnnydicamillo):

So I figure you find the derivative normally, so you get \[2(3)x^2+2x*y \frac{ dy }{ dx }-3y^2*\frac{ dy }{ ?dx} =0\]

OpenStudy (johnnydicamillo):

please excuse the question mark

OpenStudy (johnnydicamillo):

is that on the right track?

OpenStudy (freckles):

First term is right second term and third term need a little work

OpenStudy (freckles):

and the right hand side of the equation is correct of course

OpenStudy (freckles):

it looks like you are not using product rule

OpenStudy (freckles):

even know xy is a product or x^2y is a product or xy^3

OpenStudy (johnnydicamillo):

Can you show the product rule for second and third term?

OpenStudy (freckles):

\[\frac{d}{dx}(fg)=g \frac{df}{dx}+f \frac{d g}{dx}\]

OpenStudy (freckles):

\[\frac{d}{dx}(x^ny^m)=y^m \frac{d}{dx}x^n+x^n \frac{d}{dx}y^m \\=y^m \cdot nx^{n-1}+x^n \cdot m y^{m-1} y'\]

OpenStudy (freckles):

\[\text{ notice we needed the chain rule on } \frac{d}{dx}y^m=my^{m-1}y' \]

OpenStudy (johnnydicamillo):

okay, I think I am starting to understand it.

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