If T0,T1,T2,..................Tn represent the terms in the expansion of (x+a)n, then the value of (T0−T2+T4−T6+.................)2 + (T1−T3+T5−.................)2 is
Tr+1=nCrxn−r.ar
(x+ai)n=nC0xn+nC1xn−1.a.i+nC2xn−2a2.i2+....... = (T0−T2+T4−T6+.................) + (T1−T3+T5−.................)
(T0−T2+T4−T6+.................)2 + (T1−T3+T5−.................)2=(x2+a2)n