x\;\;} x{Rumpelstiltskin}$ is a valid
    (necessarily true) sentence of first-order logic.<br />

2.  Every existentially quantified sentence in first-order logic is true
    in any model that contains exactly one object.<br />

3.  ${\forall\,x,y\;\;} xy$is satisfiable.<br />
</p>
    </div>
</div>

<p><br /></p>

<div class="card">
    <div class="card-header p-2">
        <a href="ex_15/" class="p-2">Exercise 15 (Peano-completion-exercise) </a>
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