| 0 < j, 0 < j0, 0 < j1 ⊦ (rational(i, j) + rational(i0, j0)) + rational(i1, j1) = rational(i, j) + rational(i0, j0) + rational(i1, j1) |
⊦ j1 ≠ 0 ∧ j2 ≠ 0 → rational(i1, j1) + rational(i2, j2) = rational(i1 * j2 + j1 * i2, j1 * j2)
j ≠ 0 ∧ j0 ≠ 0, 0 < j, 0 < j0, 0 < j1 ⊦ rational(i * j0 + j * i0, j * j0) + rational(i1, j1) = rational(i, j) + rational(i0, j0) + rational(i1, j1)
Used terms: j0, i0, j, i