| ⊦ a ∈ ax, ∃ ax3, d1, ax2. (a0 × d)' + ax + (a × d0)' + ax1 = ax3 + (a × d1)' + ax2 ∧ ¬ a ∈ ax3 |
⊦ a ∈ ax, (a0 × d)' + ax + (a × d0)' + ax1 = ((a0 × d)' + ax) + (a × d0)' + ax1 ∧ ¬ a ∈ (a0 × d)' + ax, ∃ ax3, d1, ax2. (a0 × d)' + ax + (a × d0)' + ax1 = ax3 + (a × d1)' + ax2 ∧ ¬ a ∈ ax3
Used terms: (a0 × d)' + ax, d0, ax1