(x,y) -> xy/(x^2+y^2)
(x,y) -> 2x+y-4
(x,y) ->x^2-y^2
(x,y) ->x^2+y^2
(x,y) ->x^2-y^2
z = x^2-y^2
z = x^2+y^2
(x,y) -> xy/racine(x^2+y^2)
(x,y) -> xy/(x^2+y^2)
(x,y) -> 2x+y-4
(x,y) ->x^2-y^2
(x,y) ->x^2+y^2
(x,y) ->x^2-y^2
z = x^2-y^2
z = x^2+y^2
(x,y) -> xy/racine(x^2+y^2)