- #1
phosgene
- 146
- 1
Homework Statement
Given the function
[itex]f(x,y)=\frac{1}{2x^2 + y}[/itex]
Find the partial derivative fxx(x,y)
Homework Equations
The Attempt at a Solution
Seems pretty straight forward, just treat y as a constant and differentiate twice. But I keep getting the answer wrong and I have no idea why. Here's what I did:
[itex]\frac{∂f(x,y)}{∂x}=\frac{-4x}{(2x^2+y)^2}[/itex]
Then I differentiate with respect to x again using the quotient rule
[itex]\frac{∂^{2}f(x,y)}{∂x^{2}}=\frac{-4(2x^2+y)^2 + 4x(2(4x(2x^2 + y))}{(2x^2+ y)^4}[/itex]
I've also tried to do it by re-arranging and using the product rule, but this fails also. It's driving me mad. Have I done something wrong, or could the supposed correct answer actually be wrong?