Lemma 29.54.3. Let $f : Y \to X$ be a morphism of schemes. Assume

1. $X$ and $Y$ are affine, and

2. $f$ is quasi-finite.

Then there exists a diagram

$\xymatrix{ Y \ar[rd]_ f \ar[rr]_ j & & Z \ar[ld]^\pi \\ & X & }$

with $Z$ affine, $\pi$ finite and $j$ an open immersion.

Proof. This is Algebra, Lemma 10.122.14 reformulated in the language of schemes. $\square$

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