Partial Derivative Signs Through Level Curves

1. The problem statement, all variables and given/known data



Question 2 from http://math.berkeley.edu/~mcivor/mat...w6solution.pdf here.



I do not understand b) and e). How do I think of the slope with respect to y?



2. Relevant equations







3. The attempt at a solution



I do know that the partial derivatives are the slopes of the tanget lines. I do know that f_x < 0 as the slope is negative there (at point P), but I do not understand how the slop in terms of y looks.

via Physics Forums RSS Feed http://www.physicsforums.com/showthread.php?t=713480&goto=newpost