1. 2.1 & 2.2 Review Chapter 2 Section 3
Algebra 2 Notes
January 14, 2009

2. Warm-Ups 2.1 & 2.2 Review!!
Find the slope of the line through following points:
Find the x- and y- intercepts of the line:
Write the same equation in standard form.
Find the slope of the line perpendicular to

3. 2.3 Direct Variation
A linear function with an equation represents direct variation
is called the constant of variation
In other words, y varies directly with x.
If x is doubled then y is doubled, if x is tripled then y is tripled, etc.
Some real-world examples?

4. Identifying Direct Variation
Determine if y varies directly with x
If it does:
What is the constant of variation, k?
What is the equation of this function? x y 2 8 3 12 5 20

5. Identifying Direct Variation
Determine if y varies directly with x
If it does:
What is the constant of variation, k?
What is the equation of this function? x y 1 4 2 7 5 16

6. Identifying Direct Variation
For each function, determine if y varies directly with x
If it does:
What is the constant of variation, k?
What is the equation of the function? x y -6 -2 3 1 12 4 x y 1 4 2 7 5 16 x y 1 4 2 7 5 16

7. Identifying Direct Variation
Reminder: a function with direct variation is in the form
(Hint: what is the y-intercept??)
Determine if each of these functions represents direct variation:
If yes:
Find the constant of variation, k

8. Use a Proportion
In a direct variation function, all the x and y values are proportional to each other
For example: x y -6 -2 3 1 12 4

9. Using a Proportions
Suppose y varies directly with x, and x = 27 when y = -51. Find x when y = -17

10. More Proportions Find the missing value for each direct variation:
If y = 4 when x = 3, find y when x = 6
If y = 10 when x = -3, find x when y = 2

11. What Did We Just Cover??
A direct variation function is represented by the equation
Which means that the constant of variation is represented by the equation
The x and y values in a direct variation function are directly proportional

12. Homework #6
Pg 74 #1-4, 11-14, 17, 19, , 33, 34
READ EXAMPLE 3 ON PG 73
This will help you with #23 of your HW
2.1 – 2.3 QUIZ ON FRIDAY!!