EDB — 271

Exercises

1. [271]Let

   \[ P_ x =\{ z∈ ℕ, z{\lt} x\} \]

   show that

   \[ ∀ x,y∈ ℕ~ ,~ P_ x = P_ y ⇒ x=y \]

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

   Solution 1

   [272]↺↻

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