The coordinate plane is a grid used to plot points and draw lines. It always has the same structure, although you might only be shown part of it. The figure below shows the main components, including the axes, origin, and all four quadrants.

The Roman numerals represent the four quadrants of the plane. The origin is where the x and y axes meet. The x and y axes are used to measure the distance left or right, and up or down, where a point is located on the graph. You can think of the x-axis as a number line with 0 exactly at the center. Anything to the left is a negative number, and anything to the right is a positive number. For the y-axis, anything above the center is positive, and anything below the center is negative. The intersection of the two lines at their centers, i.e. at their 0 measurements, is the origin.

Any point on the graph can be represented by an x-value and a y-value pair. For example, the point $(1,2)$ has an $x$ measurement of $1$, a $y$ measurement of $2$, and is located in quadrant I (that’s Roman numeral 1, not a lowercase L) of the coordinate plane.

In the next chapter, we’ll discuss how a simple equation, $y=mx+b$, can represent a straight line on the coordinate plane.

Coordinate plane example question

This question is pretty basic, but it’s a good building block for more difficult ones.

Which of the following points are NOT located in Quadrant III?

Select all that apply.
A. (3, -6)
B. (-1, -1)
C. (5, 5)
D. (2, -1)
E. (-5. -2)

Give it a try!

(spoiler)

Correct choices:

A. (3, -6)

C. (5, 5)

D. (2, -1)

Here they are plotted out on the coordinate plane:

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