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## Homework Statement

f(x,y)= ln(x+y) -x^2 - y^2

1. Find the partially derivatives

2. Find the stationary points (roots) of the function

## Homework Equations

## The Attempt at a Solution

Quite simple, except i dont know what to do with the ln part, this is my attempt tho

f'x= 1/(x+y) -2x

f'y= 1/(x+y) -2y

Is this right? I am not sure what the derivative of ln (x+ c) is c= constant

2. Roots= where the function crosses the x-line right? So I simply set f'x=0 and solve it to get the root?