1. Geometry 3.6 – 3.7
Brett Solberg AHS ‘11-’12

2. Warm-up x y Find the slope of the following. 𝑚= 𝑦 2 − 𝑦 1 𝑥 2 − 𝑥 1
1) (0, 2) (2, 4) 2) (-2, 5), (4, -7)
3) Find the measure of x and y.
4) A regular polygon has an interior angle of 144˚. How many sides does the polygon have?
Do you have questions from your HW?
x y

3. Upcoming Events Today Oct 17 3.6 Wed Oct 19 3.7 Tue Oct 25 Review
Thu Oct 27 Test

4. Today’s Agenda Writing Equations Graphing Lines
Slope-Intercept Form
Standard Form
Point-Slope Form
Graphing Lines
Vertical and Horizontal Lines
graph
write

5. Slope-Intercept Form y = mx + b Graphing y = 2x - 3 m = slope
b = y-intercept
Graphing
Plot y-intercept
Use slope for 2nd point
Connect the dots
y = 2x - 3

6. Standard Form Ax + By = C Graphing 2x + 4y = 12
A, B, and C are numbers
Graphing
Set x = 0 to find the y intercept
Set y = 0 to find the x-intercept
Connect the Dots
2x + 4y = 12
If x = 0, then y = 3
If y = 0, then x = 6

7. Transforming How do you switch from Standard Form to Point-Slope Form?
2x + 4y = 8 y = -½x + 2
Solve for y.
4y = -2x + 8
y = -½x + 2

8. Point-Slope Form 𝒚− 𝒚 𝟏 = 𝒎(𝒙− 𝒙 𝟏 )
𝒚− 𝒚 𝟏 = 𝒎(𝒙− 𝒙 𝟏 )
( 𝑥 1 , 𝑦 1 ) is a point on the line
m = slope
Graphing
Plot point given in line
Use slope to plot 2nd point
Connect the dots
y – 2 = -¾(x – 4)
(4, 2)

9. Writing Equations Pick the equation that is easiest m = 2 (2, -4)
Point-Slope Form
y +4 = 2(x – 2)
m = -1 y-int = 8
Slope-Intercept Form
y = -x + 8
(2, 3) (-3, -4)
𝑚= −4−3 −3−2 = 7 5
(y – 3) = (x – 2)

10. Horizontal Lines
Lines where y is the only variable are horizontal lines.
y = mx + b
The slope is zero
y = b
Graph y =2
Graph y = -1

11. Vertical Lines Lines where x is the only variable are vertical lines.
These lines have an undefined slope.
slope = 𝑟𝑖𝑠𝑒 𝑟𝑢𝑛
run = o
Graph x = -2
Graph x = 1

12. Homework
3-6 Worksheet
Pg. 169 # 1-37 odd
graph paper on side table