2.1 & 2.2 Review Chapter 2 Section 3
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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!!