| j0 ≠ 0 ∧ j1 ≠ 0, 0 < j1, 0 < j0, 0 < j ⊦ j = 0, j0 = 0, rational(i * j0 + j * i0, j * j0) + rational(i1, j1) = rational(i, j) + rational(i0 * j1 + j0 * i1, j0 * j1) |
0 < j, 0 < j0, 0 < j1 ⊦ j0 = 0, j1 = 0, rational(i * j0 + j * i0, j * j0) + rational(i1, j1) = rational(i, j) + rational(i0 * j1 + j0 * i1, j0 * j1), j = 0