March 22, 2016
Bell Work:
1) What does direct variation look like?
2) How did we find the constant of variation?
ex. y varies directly with x. IF y = 36
when x = 8, write an equation relating x and y.
March 22, 2016
Section 8.1 ~ Model Inverse and Joint Variation
EQ: How do I recognize and find equations of inverse variation?
From a given set of data, what variation type can be determined?
Inverse Variation:
x and y vary inversely if "y varies inversely with x"
a=
Write an equation that relates x and y if they vary
inversely. Then find y when x = 2
1. x = 4, y = 3
2. YOU
x = 8,TRY!!
y = -1
March 22, 2016
What type of Variation?
a) 3x = y
b) xy = 0.75
c) y = x - 5
March 22, 2016
Check for Variation:
X
50
100
120
150
Y
24
12
10
8
What should be constant?
Is it direct?
Is it inverse?
March 22, 2016
Write an Inverse Variation Model:
The number of songs that can be stored on an
MP3 player varies inversely with the average size
of a song. A certain MP3 player can store 3000
songs with the average size of a song is 5 MB.
* Write a model that gives the number n of songs that
will fit on the MP3 player as a function of the average
song size s (in MB).
*What happens to the number of songs as
the average song size increases?
s
n
March 22, 2016
Joint Variation:
*When multiple quantities vary directly
- if z varies jointly with x and y then z = axy
WORKS with ______ or ________ quantities
Write a joint variation model if z varies jointly with x and y.
Then find z when x = -2 and y = 5.
1. z = 7 when x = 1, y = 2
2. z = 24 YOU
whenTRY!
x = 4, y = -3
March 22, 2016
What does it look like?
a) y varies inversely with x
b) z varies jointly with x, y, and r
c) y varies inversely with the square of x
d) z varies directly with y and inversely with x
e) x varies jointly with t and r and inversely with s
March 22, 2016
pg 555
#4-8, 12, 14, 20, 24, 26
Homework!
Finish from Monday: