You have
> f'(x)/f(x) = 1/g(x)
which implies
> log(f(x)) = H(x) := ∫dx/g(x)
Here, H(x) should exist on some appropriate domain which excludes any roots of g. As g is continuous, so will it's reciprocal be, and hence an antiderivative would exist. An explicit solution would be
> f(x) = C\*e^H(x)
where C comes from the constant of integration.