COORDINATE GEOMETRY
The diagram above represents the coordinate axes—the perpendicular “number lines” in the coordinate plane. The horizontal line is
called the x-axis. The vertical line is called the y-axis. In a coordinate plane, the point O at which the two axes intersect is called
the origin.
The pair of numbers, written inside parentheses, that specifies the location of a point in the coordinate plane is called coordinates.
The first number is the x-coordinate, and the second number is the y-coordinate. The origin is the zero point on both axes, with
coordinates (0, 0).
Starting at the origin:
to the right:x is positive
to the left:x is negative
up: y is positive
down: y is negativeThe two axes divide the coordinate plane into four quadrants. When you know what quadrant a point lies in, you know the signs of
its coordinates. A point in the upper left quadrant, for example, has a negative x-coordinate and a positive y-coordinate.