f/？ X=0 and? f/？ y=0

x？ -2y？ +2x=0........①

x？ -2y？ +4y=0.........②

①-②: x=2y

∴

(2y)？ -2y？ +4y=0

2y？ +4y=0

Y=0 or -2

Accordingly, x=0 or -4.

(x, y) = (0,0) or (-2, -4)

The problem cannot be resolved at this time.