# An elementary question about integration by parts! [closed]

Let $f,g: R \rightarrow R$ be two positive increasing functions. Under what (non-trivial) conditions one can guarantee that $\int_{0}^{\infty}f'g dx\geq \int_{0}^{\infty}g'fdx$.

Say, if $f/g$ is nondecreasing (plus something to take care of convergence), but that's way too strong.