1. 1234567891011121314151617181920 2122232425262728293031323334353637383940 41424344454647484950 1.f has a saddle point at (1,1) 2.f has a local minimum at (1,1) 3.f has a local maximum at (1,1)

2. 1234567891011121314151617181920 2122232425262728293031323334353637383940 41424344454647484950 1.(6, 2) 2.(3, 4) 3.(3, 2) 4.(2, 3)

3. 1234567891011121314151617181920 2122232425262728293031323334353637383940 41424344454647484950 1.(0,12) 2.(0,4) 3.(0,4.5) 4.(3,4)

4. 1234567891011121314151617181920 2122232425262728293031323334353637383940 41424344454647484950 1.(-4,4 ), (-12,12 ),(10,-10 ) 2.(-2,10 ), (-10,-12 ),(12,2 ) 3.(2,2 ), (10,10 ),(-12, 0) 4.(-2, 2 ), (-10, 10 ), (12,-12 )

5. 1234567891011121314151617181920 2122232425262728293031323334353637383940 41424344454647484950 1.(0, 0, -25) 2.(0, 0, 5) (0, 0, -5) 3.(0, 0, 25) (0, 0, -25) 4.(0, 0, 5)