⊦ ∃ i, j. ri = rational(i, j) ∧ 0 < j
∃ i, j. rj = rational(i, j) ∧ 0 < j, rational(i, j) + rj = rational(i, j) + rj0, 0 < j ⊦ rj = rj0
Used terms: rj