7.Determine the signs of the partial derivatives for the function f whose graph is shown below.

(a)    fxx(−x0, y0)

positive negative

(b)    fyy(−x0, y0)

positive negative

8. Determine the signs of the partial derivatives for the function f whose graph is shown below.

(a)    fx(−x0, y0)

positive negative

(b)    fy(−x0, y0)

positive negative

9. Determine the signs of the partial derivatives for the function f whose graph is shown below.

(a)    fx(x0, y0)

positive negative

(b)    fy(x0, y0)

positive negative

10. Determine the signs of the partial derivatives for the function f whose graph is shown below.

(a)    fxy(x0, y0)

positive negative

(b)    fxy(−x0, y0)

positive negative