If f( x , x+y , x+y+z ) = 0 and z = z( x , y ) then  what is ∂z/∂x[math] , [/math]∂z/∂y[math] , {∂}^2z/{∂x}^2 ? [/math] If f (x , x+y , x+y+z ) = 0 and z = z (x , y) then what is solution of these partials [math]\frac{∂z}{∂x} , \frac{∂z}{∂y} , \frac{{∂^2}z}{{∂x}^2} ?[/math]