# Direct Variation

#### Hayabusa

I am having alot of difficulty with this problem . I don't have the slightest idea on how to do this problem and my textbook does not explain it. Please help me:

Determine whether 1 - y = 2x is a direct variation. If so explain.

This problem has me stumpted and very frustrated.

#### whozum

A relationship between two variables such that the data increase or decrease together at a constant rate is called direct variation.

When x increases or decreases, what happens to y?
Is there a constant relationship between x and y?

#### HallsofIvy

Homework Helper
It never ceases to amaze me that people think they should be able to do a problem in which they don't know what the key words mean.

The whole point of this question is the definition "direct variation". As whozum said "A relationship between two variables such that the data increase or decrease together at a constant rate is called direct variation.
(I emphasized the crucial part.)

Whozum then asks "When x increases or decreases, what happens to y?
Is there a constant relationship between x and y?". I'll be more specific: when x= 1 what is y? When x doubles to 2, what is y? Did y also double? Is this "direct variation"?

#### Hayabusa

I don't mean to be a pest, but I still do not comprehend how to do this problem. Can I get a little more help.

#### HallsofIvy

Homework Helper
Start by answering as many of the questions I asked as you can!

#### Hayabusa

I know what the words mean, I just don't know how to solve the problem. I read the same definitions in the chapter. But the book doesn't show me how to solve the problem. If you can be so kind and help me start the problem I'd appreciate it.

#### HallsofIvy

Homework Helper
Alright, I'll give you one more chance!
What is f(1)?

What is f(2)?

2 is exactly twice 1. Is f(2) exactly twice f(1)?

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