Computing ∂f/∂x (0,0) | Midterm Review Sheet Problem 2(a)

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SUMMARY

The discussion focuses on computing the partial derivative ∂f/∂x at the point (0,0) for the function defined in problem 2(a) of the midterm review sheet. The user correctly applies the quotient rule to derive the expression for ∂f/∂x, which is given by [(x²+y²)(y²)-(xy²)(2x)]/[x²+y²]². The user identifies that direct substitution at (0,0) is not feasible and considers evaluating the limit as (x,y) approaches (0,0) instead. Ultimately, the user concludes that ∂f/∂x|x=0 equals 1, leading to the final evaluation of (∂f/∂x|x=0)|y=0 also being 1.

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Homework Statement



This is problem 2(a) from my midterm review sheet, found here: http://www.math.washington.edu/~sullivan/326smt_sp10.pdf

Homework Equations



Not sure what exactly I need here

The Attempt at a Solution



By the quotient rule, ∂f/∂x = [(x2+y2)(y2)-(xy2)(2x)]/[x2+y2]2. Obviously I can't just plug in (0,0). I thought about computing lim(x,y)-->(0,0) f(x,y), but the limit does exist, and doing that seems to be saved for part (b). Is there some theorem I should use to compute ∂f/∂x|(0,0)?

Thank you for for help.
 
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OH! I think I might be on to something. I could first evaluate ∂f/∂x|x=0 , and then (∂f/∂x|x=0)|y=0.

∂f/∂x|x=0 = y4/y4 = 1 ---> (∂f/∂x|x=0)|y=0 = 1.

Right?
 

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