EDB — 271

Exercises

1. [271]Let

   $$P_x=\{z\in \mathbb{N},z<x\}$$

   show that

   $$\forall x,y\in \mathbb{N},P_x=P_y\Rightarrow x=y$$

   using the properties in Hypothesis [26H]↺↻.

   Solution 1

   [272]↺↻

   (Note the similarity with [26S]↺↻).