This video introduces the parametric form of a ray in 2D. [Click here](/v/weighted-average-two-points) to review weighted averages of 2 points. [Click here](/math/algebra/two-var-linear-equations-and-intro-to-functions/slope-intercept-form/v/slope-intercept-form) to review slope-intercept form of a line.
License: CC BY-NC-SA by Khan Academy