1. Writing Equations
Objective: By the end of this section students will be able to write the equation of line from word problems, tables and scatter plots.

2. Equation of a line
Standard form Ax + By = C Slope Intercept Y=mx+b Point Slope (y-y)=m(x-x)

3. Slope Intercept
Y=mx+b What do the letters stand for? y y coordinate of any point on the line m slope of the line, keep as a fraction x x coordinate of any point on the line b the y intercept, where line crosses the y axis

4. Given an Equation
Solving for y Get all y terms on one side of the equation Get all other terms on opposite side of the equation These are usually done with addition or subtraction Divide by coeficient of y term

5. Example
2x-4y= y+3x-20=0

6. Given Graph
Find slope between 2 points Find where line crosses y axis Write the equation

7. Example
If x and y axis are counting by ones, find the equation of the line

8. Given Slope and y int
If you are given the slope and y-int just substitute those values into the equation M=2/3 B=4 or (0,4) Y=2/3x+4

9. Example

10. Slope and a point
You need to calculate the y-int Sub the slope in for m and the ordered pair in for x and y Calculate the value of b substitute those values into the equation

11. Example

12. 2 Points
Calculate the slope Calculate the y-int Write equation

13. Example

14. Other Parts of Lines
How could you calculate the x-intercept? Set y=0 and solve for x Graph it and find point How could you calculate the y-intercept? Set x=0 and solve for y Solve for y and look for b

15. Example
Calculate the x and y intercepts

16. Homework
Worksheet on equations of lines in slope intercept form Finding x and y intercepts