Question

A direct variation function contains the points (–9, –3) and (–12, –4). Which equation represents the function?

y = –3x
y = – x/3
y = x/3
y = 3x

C is the correct answer.

Answer 1

Answer: third option.

Explanation:

By definition, a direct variation function has the form shown below:

`y=kx`

Where k is a constant.

Then, knowing the given points, you can calculate k with the formula for calculate the slope of a line:

`m=(y_2-y_1)/(x_2-x_1)=(-4-(-3))/(-12-(-9))=(1)/(3)`

Substituting k into
`y=kx`, you obtain:

`y=(1)/(3)x\\\\y=(x)/(3)`