For (x² + a²)⁵,

a= x², b= a² and n=5

As n is odd, there are two middle terms i.e.

I. and II.

General term t_r+1 is given by,

I. The first, middle term is

Therefore, for the 3^rd middle term, r=2

Therefore, the first middle term is

= 10. a⁴. x⁶

II. The second middle term is

Therefore, for the 4^th middle term, r=3

Therefore, the second middle term is

………

= 10. a⁶. x⁴