A linear function / slope-intercept form is …
y = mx + b
A linear function in standard form is …
Ax + By = C
The formula for the slope (m) is …
(y1-y2)/(x1-x2)
An undefined slope is …
A directly vertical line
You can find the slope of a line by …
Using any two points on that line
Point-Slope form is …
y - y1 = m(x - x1)