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 = 2xcan be written asy = 2x + 1

I beleive that the '+ 1' makes the equationnot 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.