From the given condition, replacing a by ai
and −ai respectively, we get (x+ai)n=(T0−T2+T4−......)+i(T1−T3+T5−.....) .....(i)
and (x−ai)n=(T0−T2+T4−.....)−i(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