By direct calculation, it is not difficult to conclude that the constrained maximum is f = 2 , with solutions ( x , y ) = ( 2 2 , 2 2 ) and ( x , y ) = ( − − 2 2 , − − 2 2 ) , while the constrained minimum is f = 0 , with solutions ( x , y ) = ( − − 2 2 , 2 2 ) and ( x , y ) = ( 2 2 , − − 2 2 ) .