#### Answer

(a) Negative
(b) Negative

#### Work Step by Step

(a) The value of $z$ of the graph decreases at the point $(-1, 2)$ as the value of $x$ increases from the point along the x- axis, this represents the negative values of $f_{x}$.
Thus,$f_{x} (-1,2)$ is negative.
(b) The value of $z$ of the graph decreases as the value of $y$ increases near the point $(-1, 2)$ , this represents the negative values of $f_{y}$.
Thus,$f_{y} (-1,2)$ is negative.