## Algebra and Trigonometry 10th Edition

First quadrant: $x\gt0$ and $y\gt0$ Second quadrant: $x\lt0$ and $y\gt0$ Third quadrant: $x\lt0$ and $y\lt0$ Fourth quadrant: $x\gt0$ and $y\lt0$ We have a point $(x,y)$ such that: $x+y=0,~~x\ne0,~~y\ne0$ $x=-y$ That is: - if $y\gt0$, then $x\lt0$ -> Second quadrant - if $y\lt0$, then $x\gt0$ -> Fourth quadrant