Lemma 70.18.7. Let $S$ be a scheme. Let $B$ be an algebraic space over $S$. Let $Z \subset B$ be a closed subspace. Let $b : B' \to B$ be the blowing up with center $Z$. Let $Z' \subset B'$ be a closed subspace. Let $B'' \to B'$ be the blowing up with center $Z'$. Let $Y \subset B$ be a closed subscheme such that $|Y| = |Z| \cup |b|(|Z'|)$ and the composition $B'' \to B$ is isomorphic to the blowing up of $B$ in $Y$. In this situation, given any scheme $X$ over $B$ and $\mathcal{F} \in \mathit{QCoh}(\mathcal{O}_ X)$ we have

the strict transform of $\mathcal{F}$ with respect to the blowing up of $B$ in $Y$ is equal to the strict transform with respect to the blowup $B'' \to B'$ in $Z'$ of the strict transform of $\mathcal{F}$ with respect to the blowup $B' \to B$ of $B$ in $Z$, and

the strict transform of $X$ with respect to the blowing up of $B$ in $Y$ is equal to the strict transform with respect to the blowup $B'' \to B'$ in $Z'$ of the strict transform of $X$ with respect to the blowup $B' \to B$ of $B$ in $Z$.

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