Linear function
Linear function graph
The graph of a linear function is a straight line. Two correctly calculated points are enough to draw the whole function.
Value table
Two points
Line on the coordinate plane
Check your knowledge
A short quiz will help you quickly spot which concepts are worth reviewing.
How do you draw the graph?
- 1Choose two or three convenient x values.
- 2Substitute them into the formula and calculate the y values.
- 3Mark the points on the coordinate plane.
- 4Connect the points with one straight line.
Value table
For the function y = 2x + 2, we choose three simple x values and calculate the corresponding y values.
| x | y = 2x + 2 | Point |
|---|---|---|
| -1 | 0 | (-1, 0) |
| 0 | 2 | (0, 2) |
| 1 | 4 | (1, 4) |
Function on the graph
The points from the table lie on one straight line because a linear function has a constant rate of change.
In this example, every increase of x by 1 increases y by 2.
y = 2x + 2
Go to the zero of a function