From the given condition, replacing a by ai and – ai respectively, we get (x−ai)n = (T0−T2+T4−...) + (T1−T3+T5−...) ... (i) and (x−ai)n = (T0−T2+T4−...) + (T1−T3+T5−...) ... (ii) Multiplying (ii) and (i) we get required result i.e., (x2+a2)n = (T0−T2+T4−...)2 + (T1−T3+T5−...)2