Find all relative extrema for the function, and then match the equation to its graph.
z = -x4 + y4 + 2x2 - 2y2 + 
A. Relative maxima of 
at (1, 1) and
at (-1, -1); saddle point at (0, 0)
B. Relative minima of - 
at (0, 1) and
at (0, -1); saddle point at (0, 0)
C. Saddle points at (0, 0), (-1, 1), (1, -1), (1, 1),
and (-1, -1)
D. Relative maxima of 
at (-1, 1) and
at (1, 1)
Answer: C
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A. 
B. 
C. 
D. 
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