Intermediate · 12 min
Coordinates and straight lines
Use coordinate pairs and calculate the slope of a straight line.
Read coordinates in order
In (x, y), x gives horizontal position and y gives vertical position. A negative coordinate places a point left of or below the origin.
Worked example
(−2, 3) is 2 units left and 3 units up from (0, 0).
Calculate slope
Slope is the change in y divided by the change in x. Use the same point order for both changes. Vertical lines have no finite slope.
Worked example
From (1, 2) to (4, 8): slope = (8 − 2) ÷ (4 − 1) = 2
Build a line from points
- Make a table of y = 2x + 1 for x = 0, 1, 2, and 3.
- Plot the points and explain how the slope appears in the table.