Correct option: (d) 9
Explanation:
Tr+1 = ncr an–r br
∴ Tr+1 = 10cr (3 / x2)10–r (√x / 3)r
= 10cr (310–r ∙ 3–r) (x(x/2) ∙ x–20+2r)
= 10cr (310–2r) (x(5r/2)–20)
To have constant term, x(5r / 2) – 20 = x0
i.e. (5r / 2) – 20 = 0
∴ 5r = 40
∴ r = 8
∴ Tr+1 = T9 = i.e. 9th term is constant