Question

Which of the following functions is a direct variation?

f(x) = 2x
f(x) = x + 2
f(x) = 2

Answer 1

When two variable quantities have a constant (unchanged) ratio, their relationship is called a direct variation. It is said that one variable "varies directly" as the other...simply when the y-intercept is zero.

So the best answer is f(x)=2x

Answer 2

`f(x)=2x`

Explanation:

we know that

A relationship between two variables, x, and y, represent a direct variation if it can be expressed in the form
`y/x=k` or
`y=kx`

In a direct variation the constant of proportionality k is equal to the slope of the line m and the line passes through the origin

therefore

in this problem

`f(x)=2x` -----> represent a direct variation