2.2 ­ Direct Variation.notebook
September 26, 2013
2.2 ­ Direct Variation.notebook
September 26, 2013
2.2 ­ DIRECT VARIATION
• If you have a job that pays you $8/hour, how much
money will you make if you work 13 hours?
• How much will you make if you work 20 hours?
This is an example of direct variation . When one
quantity goes up, the other quantity also goes up. It
can be written as:
where k is called the constant of variation .
EXAMPLES
Does the given equation display direct variation? (Hint: solve for y)
(a)
(b)
(c)
EXAMPLES
Determine whether y varies directly with x. If so, what is the constant of variation and the function rule?
x
3
2
1
y
­21
­14
­7
x
2
3
6
y
5
7
13
.
2.2 ­ Direct Variation.notebook
September 26, 2013
EXAMPLES
The variables x and y vary directly, and y = 15
when x = 3.
­Write an equation that relates x and y.
­Find y when x = ­4 A salesperson's commission varies directly with sales. For $1000 in sales, the commission is $85. What is the commission for $2300 in sales?
The graph of a direct variation function is always a line through the origin .
EXAMPLE ­ What is the graph of the direct variation situation described?
Graph goes through the point: (7, 2)
HOMEWORK: MathXL Online