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Is the following equation a DIRECT VARIATION function?
y = x 

Definition
YES! (Because it is in the form "y = kx" where k = 1) 


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Definition
DIRECT VARIATION (Because the graph goes through the origin!) 


Term

Definition
NOT DIRECT VARIATION (Graph does not go through the origin!) 


Term

Definition
DIRECT VARIATION (Graph goes throught the origin!) 


Term

Definition
NOT DIRECT VARIATION (Graph does not go through the origin!) 


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Definition
DIRECT VARIATION (Graph goes through the origin!) 


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Is the following equation a DIRECT VARIATION function?
y = 3x 

Definition
YES! (Because it is in the form "y = kx" where k = 3) 


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Is the following equation a DIRECT VARIATION function?
y = x + 2 

Definition
NO!
(Because direct variation functions never have addition or subtraction in them..They should be in the form "y = kx") 


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What is the CONSTANT OF VARIATION for y = 6x? 

Definition
The CONSTANT OF VARIATION (k) is 6! 


Term
If the point (2, 8) is on a direct variation function, what is the CONSTANT OF VARIATION? 

Definition
SOLUTION:
Direct Variation Equation: y = kx
The point (2, 8) is an (x, y)
Replace x and y in the equation for the x & y coordinates:
8 = k(2)
Divide by 2 on both sides to get:
k = 4


