A function f(x,y)=x3−3xy+y3f(x, y) = x^3 - 3xy + y^3f(x,y)=x3−3xy+y3 has a critical point. Which of the following is true?
(0,0)(0, 0)(0,0) is a local maximum
(1,1)(1, 1)(1,1) is a local minimum
(1,1)(1, 1)(1,1) is a saddle point
There are no critical points