Write Linear Equations Chapter 9 Lesson 2 Write Linear Equations Pg. 685

What we Know so far…. Direct Variation Where k is the slope and Slope Intercept Form Where k is the slope and “0” (origin) is the y-intercept Where m is the slope and b is the y-intercept In order to graph a line, we need the slope and a point

Where two points are given as (x1,y1) and (x2,y2) What we Know so far…. Slope Where two points are given as (x1,y1) and (x2,y2)

The Old Stuff… Writing equations Slope-intercept form is: Where m is the slope and b is the y-intercept Example: Find the equation of the line with “m” = slope = -2 and “b” = y-intercept = 8 y = -2x + 8 Easy if I know the y-intercept… but if I don’t?

The New Stuff… Point - Slope Form Point - Slope form is: Where m is the slope and (x1,y1) is the given point that the line goes through

The New Stuff… Point- Slope Form Point- Slope form is: Where does this equation come from? The Slope Formula

The New Stuff… Point- Slope Form Point- Slope form is: Attached to the “x” is the “x-coordinate” Attached to the “y” is the “y-coordinate” m = 5 , (4, 7) m = -2 , (4, - 7)

m = -5, (-3, 2) m = , (8, -4)

If you are given the equation in Remember…. If you are given the equation in Point-Slope Form, and you are asked to graph, the (x1, y1) are opposite from how they appear.

Using Point-Slope Form to graph 1 2 4 3 5 -1 -2 -3 -4 -5 Slope is Point is (2,3)

Change Point-Slope Form to Slope-Intercept form

Change Point-Slope Form to Slope-Intercept form

Your turn m = (1, 1)

Your turn m = ( -3, 4)

What do we do if they give 2 Points (-3, 6) and (1, -2)?

Homework Pg. 689 - 691 RC: 1 – 11, 14 HC: 1 – 14