Chapter 8.3, Problem 39P

To determine

(a)

To find:

The sign of $f_y\left(P\right)$, since $f_x\left(P\right)>0$ for a function $f\left(x,y\right)$.

To determine

(b)

To find:

The sign of $f_y\left(Q\right)$, since $f_x\left(P\right)>0$ for a function $f\left(x,y\right)$.

To determine

(c)

To find:

The sign of $f_x\left(Q\right)$, since $f_x\left(P\right)>0$ for a function $f\left(x,y\right)$.