What is the domain of this function sketch the domain as a

Question

Let f(x,y) = √(x² + y² - 9).

a. What is the domain of this function? Sketch the domain as a region in the xy plane.

b. Write parametric equations for the intersection of this function with the function g(x, y) = x + y.

c. Give the equations of the traces of this function [f{x, y), that is] in the xy, xz, and yz planes, and sketch the traces.

d. Find f_x(x, y)and f_y(x, y).