Answer
1. First graph of Figure 17
The point is a saddle point.
2. Second graph of Figure 17
The point is not a local minima nor local maxima. It is neither a saddle point.
3. Third graph of Figure 17
The left point is a local minimum.
The right point is a local maximum.
Work Step by Step
1. First graph of Figure 17
If we walk in the directions $ + {\bf{i}}$ or $ - {\bf{i}}$, it will take us downhill. If we walk in the directions $ + {\bf{j}}$ or $ - {\bf{j}}$, it will take us uphill. Therefore, we conclude that it is a saddle point.
2. Second graph of Figure 17
If we walk in these directions:
$ + {\bf{i}}$, it will take us uphill
$ - {\bf{i}}$, it will take us downhill
$ + {\bf{j}}$ or $ - {\bf{j}}$, it is neither downhill nor uphill
Therefore, we conclude that it is not a local minima nor local maxima. It is neither a saddle point.
3. Third graph of Figure 17
The left point is a local minimum, because no matter which direction we walk, it will take us uphill.
The right point is a local maximum, because no matter which direction we walk, it will take us downhill.