Consider an integral such that $$ \int_{0^+}^\infty f(x) \, dx = C,$$where, $f(x)$ is a smooth and continuous function and absolutely converges.
Now we raise both sides to the power s:
$$\left(\int_{0^+}^\infty f(x) \, dx\right)^s = C^s $$
We substitute $x$ with $rx$ to get:
$$\left(\int_{0^+}^\infty f(rx) \, dx\right)^s = (C/r)^s $$
Multiplying both sides by an arbitrary coefficient:
$$ (b_r)\left(\int_{0^+}^\infty f(rx) \, dx\right)^s = (b_r)( C/r)^s $$
Taking their sum:
$$ \sum_{r=1}^\infty b_r \left(\int_{0^+}^\infty f(rx) \, dx\right)^s = C^s \underbrace{\sum_{r=1}^\infty \frac…