X y 39
6 18
9 27
12 36
21) The table shows a proportional relationship between x and y, What is the unit rate of y per x?
A) 1
B) 3
C) 6
D) 9

Step-by-step explanation:

the unit rate of y per x :

9/3 = 18/6 = 27/9 = 36/12

all the results = 3

the right answer is B) 3

the direct variation says that:

then the equation is of the form is given by:

            where k is the constant variation.

from the given table:

consider any value of x and m(x)=y

x = 2 and m(x)=y = 3

substitute these value in [1]; we have;

divide both sides by 2 we get;

⇒

check:

put x = -1 and m(x) = -1.5

substitute in the equation:

-1.5 = -1.5                   true

therefore, the function m(x) represents a direct variation

graph of this function as shown below: