There are only a couple more items to cover relating to lines, so the notes for today will not be too long. However, the material from Days 8 and 9 are absolutely essential, and will be showing up in (nearly) every future math class you take — this is a good opportunity to make sure you understand it thoroughly and get your questions answered.

**Horizontal and vertical lines** are particularly simple — so simple, in fact, that they can be a little confusing. This video does a good job of explaining the graphs and equations of horizontal and vertical lines.

We saw last time how to write an equation for a line if we know the slope *m* and the y-intercept *b* (using the *slope-intercept form*, y=mx+b). It is often the case that we do not know the y-intercept, but instead we know a different point on the line. In this case, there is a shortcut that we can use to find the equation of the line — the **point-slope form** of a line, which is *y-y1=m(x-x1) *(*m* still represents the slope, and (x1, y1) is simply *any* point on the line).

This video gives some examples of writing equations of lines in point-slope form, and also talks about the similarities and differences between point-slope form and slope-intercept form.

Videos are helpful, keep posting them please.

John

Prof. Reitz

i agree with Shakira videos help a lot.

Pro. Halleck

Just watch the video, yeah it does help, after watching this video I understand it a bit more.