Answer
A diagonal plane that contains the y-axis and makes a 45-degree angle with both the yz- and xy-planes. It lies in the two upper-front octants and the two lower-back octants.
Work Step by Step
The given equation does not include $y$, so $y$ can take on every possible value. This means our region will extend infinitely along the y-axis. If we consider a fixed value of $y$, say $y = 0$, we get a line in the xz-plane with slope 1 through the origin. Our region will therefore be made up of infinite copies of this line, one for every value of $y$. Putting all these lines together, we get a diagonal plane, that contains the entire y-axis and makes a 45-degree angle with both the yz- and xy-planes. It lies in the two upper-front octants and the two lower-back octants.
