fx=2x−2xy
fy=4y−x2
fx=0fy=0
2x−2xy=04y−x2=0If x=0, then y=0.
If y=1, then x=−2 or x=2.
Point (0,0), Point(-2, 1), Point(2, 1).
fxx=2−2y,fyy=4,fxy=fyx=−2x
D=∣∣2−2y−2x−2x4∣∣=8−8y−4x2 Point (0,0)
D=8−0−0=8>0
fxx(0,0)=2>0Then f(0,0) is a local minimum.
Point (-2,1)
D=8−8−16=−16<0 Then f(−2,1) is a saddle point.
Point (2,1)
D=8−8−16=−16<0 Then f(2,1) is a saddle point.
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