The sum of rational terms in the expansion of is
(r + 1)th term in the given expansion is given by
where r = 0, 1, 2, ..., 10
For rational terms
r = a multiple of 5 = 0, 5, 10……..(1)
10 – r = a multiple of 2 = 0, 2, 4, 6, 8, 10 ……...(2)
From Eq. (1) and (2) possible values of r are : 0 and 10
∴ sum of rational terms