Answer:
The maximum of the function is at [tex]x=1 , y=2[/tex]
Step-by-step explanation:
Remember at that the maximum and minimum of a multivarable function
[tex]\nabla f = 0[/tex]
For this case
[tex]\nabla f = ( 3x^2 -3 , -3y^2 + 12 ) = ( 0,0)[/tex]
Therefore you have to solve the equations
[tex]3x^2 -3 = 0\\-3y^2 +12 = 0[/tex]
Solving the equations you get [tex]x = 1 , y = 2[/tex] , and those points are located at the quadrilateral given.
There are no more critical points.