syms A B C x y;
>> dsolve('Dy=A-B*y-C*x*y','x')
ans =
-1/2*A*erf(1/2*(-2*C)^(1/2)*x-B/(-2*C)^(1/2))*exp(-1/2*x*(2*B+C*x)-1/2*B^2/C)/C*2^(1/2)*(-pi*C)^(1/2)+exp(-1/2*x*(2*B+C*x))*C1