Algebra – Part 7: Equation of a Line in Point-slope-form

There are two methods for writing the equation of a line: point-slope form and slope-intercept form. Both methods require knowledge of at least two pieces of information about the line.

1. A point
2. Another point
3. The slope, m
4. The y-intercept, b (the y-coordinate of the point at which the graph of the line crosses the y-axis)

If you know any two of these things, you can find the equation of the line.

The equation of a line in point-slope form:

y − y1 = m(x − x1)

In this form, (x1, y1) is a point on the line, and m is the slope. To use this form
when you know two points on the line but you don’t know the slope, first
find m using the previously seen formula:

To use the point-slope form of the equation of a line, you need to have the slope (m) and the coordinates of one point (x1, y1). Once you have this information, simply plug it into the point-slope form of the equation.

Sample 1:

Sample 2:

Sample 3: