I am interested in making a set of equations more useful, but I can't seem to think of/remember if there is a way.

I want to find the numbers not hit by a set of equations.

The equations are simple, but I don't see a way to solve the equations, only comparing results

For instance

11x+4

12x+11

17x+12

19x+1

--2,3,5 through 10,13,14 aren't hit.

Im not interested in whether they cross paths on a graph, only the integer values they produce.

Is there a way to solve for the integer values that aren't reached? Or perhaps just check one integer for all the equations at once. I know its simple now, but if I have dozens or hundreds of these, I'd like to be able to simplify.

Thanks!