differential equation with f(x)*y(x)

Hi,

I am trying to solve a set of coupled 1st order differential equations 
which include terms of the type  f(y)*y(x) with Maxima 5.26.0:

test: 'diff(y(x),x)+f(x)*y(x)=a;
atvalue(y(x),x=0,1);
desolve(test,y(x));

The result I am getting is:

y(x)=ilt((( laplace( f(x)y(x), x,  g1990 )-1) g1990 a)/g1990^2 , g1990, x )

or, in the case of the specific function f(x):=exp(-x^2), a:0:

y(x)= ilt ( ( laplace(  exp(-x^2)y(x), x,  g2042 ) -1 )/g2042 , g2042, x )

How do I go from here to find the solution?

In the latter case, Mathematica, returns the solution 
y(x)=exp( -sqrt(%pi)/2*erf(x) ), 
and in the former an expression involving exponentials of 
integrals of f(x).

Thanks for your help,
Bertold