I try to solve IVP for ode $$ \dot{x} = f(t)g(x,t). $$
The $f(t)$ is relative simple and it is easy to get information about $\int fdt$ and $\frac{df}{dt}$.
I want to find a transformation $y=y(x)$ or $y=y(x, t)$ such that $$ \dot{y} = g(y, t). $$
My question is does such $y$ exist? If exists, what is the formula?