Dann entspricht der Regel „a + (b + 1) = (a + b) + 1” die Form1
a + (1 + 1) = (a + 1) + 1
            a + (ξ + 1) = (a + ξ) + 1
‒ ‒ ‒ S

a + ((ξ + 1) + 1) = ((a + ξ) + 1) + 1(Ƒ)

der Regel R.

Editorial notes

1) Deleted formulas.