Find the local maximum and minimum values and saddle point(s) of the function. You are encouraged to use a calculator or computer to graph the function with a domain and viewpoint that reveals all the important aspects of the function. (Enter your answers as comma-separated lists. If an answer does not exist, enter DNE.)
f(x, y) = 2x^3 + xy^2 + 5x^2 + y^2 + 6
local maximum value(s)
local minimum value(s)
saddle point(s)
(x,y) = (-1,2), (-1,-2)