Basic question about differential equation

[kougou]

Homework Statement

dy/dx +y=x

Homework Equations

none

The Attempt at a Solution

We know that x is the independent variable because y is differentiate with respect to it. And y is the dependent variable. Just wondering do you guys know why y is always a function of x in these kinds of differential equation? I got confuse when somebody write like dy(x)/dx+y(x)=x. How do you know y is always a function of x?

Thank you

 

[Bohrok]

It's usually understood what the independent variable is in a given differential equation from the context; often it's either x or t when dealing with one independent variable.