## Thomas' Calculus 13th Edition

a. Domain : The set of all $(x,y)$ when $y -x \geq 0 \implies y \geq x$. b. Range is given as: $z\geq 0$ c. Level Curves: These are straight lines $y-x=c$ and parallel to the line $y=x$ d. Boundary point is $\sqrt {y-x} =0$ and a straight line such as $y=x$ e. Closed f. Unbounded