#### Answer

3, -2

#### Work Step by Step

(a) The slope of the line tangent to a surface $f(x,y)$ at the point $(a,b)$ and lying in the plane $x=a$ is given as $f_y(a,b)$.
Thus, $f_y(x,y)=3y^2 \implies
f_y(-1,1)=3 \cdot 1^2=3$
(b) The slope of the line tangent to a surface $f(x,y)$ at the point $(a,b)$ and lying in the plane $y=b$ is given as $f_x(ab)$.
Thus, $f_x(x,y)=2x \implies f_x(-2,1)=2 (-1)=-2$