## Equation and Point-slope-form

Here are some formulas you need to remember to solve new challenges!

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.

- A point
- Another point
- The slope, m
- 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.