∀ a, d. ax0[a, d][a] = d ⊦ a = a0, ax0[a, d][a] = d
Used simplifier rules: assoc-no: ⊦ a ≠ b → ((b × d)' + ax)[a] = ax[a];% ⊦ (ax + ax0) + ax1 = ax + ax0 + ax1;