Explore the Properties of a Straight Line Graph

The equation of a straight line is usually written as:

y = mx + b

Where m is the slope (how steep the line is) and b is the y-intercept (where the line crosses the y-axis).

Move the m and b slider bars as you please:

../algebra/images/graph-straight-line.js

Read more about the Equation of a Straight Line

Things to try:

The effect of changes in m
The effect of changes in b
The effect of a negative value of m
The effect of a negative value of b
How to create a horizontal line

Find the Equation from 2 Points

Now see how two points can change the line equation. Try to make:

y = x
y = x + 2
y = −2x + 8
y = 4
x = 4

../geometry/images/geom-line-equn.js?mode=equn

When we try to make, say, x = 4 we get a vertical line. A vertical line is special because its slope is undefined, so we can't write it as y = mx + b