| ∀ a, b. (x0 -l a) -l b = (x0 -l b) -l a ⊦ a = a0, (a0 ' + (x0 -l a)) -l b = ((a0 ' + x0) -l b) -l a |
b = a0, ∀ a, b. (x0 -l a) -l b = (x0 -l b) -l a ⊦ a = a0, (a0 ' + (x0 -l a)) -l b = ((a0 ' + x0) -l b) -l a
∀ a, b. (x0 -l a) -l b = (x0 -l b) -l a ⊦ b = a0, a = a0, (a0 ' + (x0 -l a)) -l b = ((a0 ' + x0) -l b) -l a
Used formulas: b = a0