Find the local maximum and minimum values and saddle point(s) ofthe function. If you have three-dimensional graphing software,graph the function with a domain and viewpoint that reveal all theimportant aspects of the function. (Enter your answers as acomma-separated list. If an answer does not exist, enter DNE.)

f (x, y) = xy ? 3x? 3y ? x² ? y²

local maximum value(s)
local minimum value(s)
saddle point(s)	(x, y, f)	=

Find the local maximum and minimum values and saddle point(s) ofthe function. If you have three-dimensional graphing software,graph the function with a domain and viewpoint that reveal all theimportant aspects of the function. (Enter your answers as acomma-separated list. If an answer does not exist, enter DNE.)

f(x, y) = 3x³ ?9x + 9xy²

local maximum value(s)
local minimum value(s)
saddle point(s)		(x, y, f) =

Find the local maximum and minimum values and saddle point(s) ofthe function. If you have three-dimensional graphing software,graph the function with a domain and viewpoint that reveal all theimportant aspects of the function. (Enter your answers as acomma-separated list. If an answer does not exist, enter DNE.)

f(x, y) = 7 ? x⁴+ 2x² ? y²

local maximum value(s)
local minimum value(s)
saddle point(s)		(x, y, f) =

Find the local maximum and minimum values and saddle point(s) ofthe function. If you have three-dimensional graphing software,graph the function with a domain and viewpoint that reveal all theimportant aspects of the function. (Enter your answers as acomma-separated list. If an answer does not exist, enter DNE.)

f (x, y) = x² +xy + y² + 5y

local maximum value(s)
local minimum value(s)
saddle point(s)	(x, y, f)	=