When two variable quantities have a constant (unchanged) ratio, their relationship is called a direct variation.
The general form of a direct variation is y = kx, where k is the constant of variation which describes the relationship between variables y and x.
1 - y = 2x can be written as y = 2x + 1
I beleive that the '+ 1' makes the equation not a direct variation.
A test for checking the situation could be as follows:
If you double x and y also doubles then it is a direct variation. In this case it is not.