Let $M = (X, \mathcal{F}, \mu)$ be a D1158: Measure space.
Let $f, g: X \to [0, \infty]$ each be a D313: Measurable function on $M$.
Let $\alpha, \beta \in [0, \infty)$ each be an D4767: Unsigned real number.
Let $f, g: X \to [0, \infty]$ each be a D313: Measurable function on $M$.
Let $\alpha, \beta \in [0, \infty)$ each be an D4767: Unsigned real number.
Then
\begin{equation}
\mu(\alpha f + \beta g)
= \alpha \mu(f) + \beta \mu(g)
\end{equation}