Given expansion is (1 + x2 )8
(1 + x2 )8 = 1 + 8C1 (1)8 – 1 (x2 )1 + 8C2 (1)8 – 2 (x2 ) 2 + 8C3 (1)8 – 3 (x2) 3 +8C4 (1)8 – 4 (x2 ) 4 + 8C5 (1)8 – 5 (x2 )5 + 8C6 (1)8 – 6x2 )6 +8C7 (1)8 – 7 (x2 )7 +8C8 (1)8 – 8 (x2)8
= 1 + 8x2 + 28x4 + 56x6 + 70x8 + 56x0 + 28x2 + 8x4 + x16
Coefficient of x6= 56
Coefficient of x4 = 28
∴ Different between the coefficients of x6 and x4
= 56 – 28 = 28