1. The problem statement, all variables and given/known data f(x,y)= ln(x+y) -x^2 - y^2 1. Find the partially derivatives 2. Find the stationary points (roots) of the function 2. Relevant equations 3. 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?