2.1 & 2.2 ReviewChapter 2 Section 3Algebra 2 NotesJanuary 14, 2009

Warm-Ups2.1 & 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

2.3 Direct VariationA 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?

Identifying Direct VariationDetermine if y varies directly with

x

If it does:◦What is the constant of variation, k?◦What is the equation of this function?

x y2 83 125 20

Identifying Direct VariationDetermine if y varies directly with

x

If it does:◦What is the constant of variation, k?◦What is the equation of this function?

x y1 42 75 16

Identifying Direct VariationFor 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 y1 42 75 16

x y1 42 75 16

x y-6 -23 1

12 4

Identifying Direct VariationReminder: 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

Use a ProportionIn a direct variation function, all the x

and y values are proportional to each other

For example:x y-6 -23 1

12 4

Using a Proportions

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

More ProportionsFind 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

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

Homework #6Pg 74 #1-4, 11-14, 17, 19, 23-25, 33, 34

READ EXAMPLE 3 ON PG 73◦This will help you with #23 of your HW

2.1 – 2.3 QUIZ ON FRIDAY!!