| a0 ∈ x0, ∀ a. rmdup(x0 + a ') = rmdup(x0 -l a) + a ' ⊦ a = a0, rmdup(x0 + a ') = rmdup(a0 ' + (x0 -l a)) + a ' |
⊦ rmdup(a ' + x) = (a ∈ x ⊃ rmdup(x);a ' + rmdup(x))
a0 ∈ x0, ∀ a. rmdup(x0 + a ') = rmdup(x0 -l a) + a ' ⊦ a = a0, rmdup(x0 + a ') = (a0 ∈ x0 -l a ⊃ rmdup(x0 -l a);a0 ' + rmdup(x0 -l a)) + a '
Used terms: x0 -l a, a0