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Question:

The total number of irrational terms in the binomial expansion of (7^(1/5))⁶⁰ is:

55

49

48

54

Solution:

Given (7^(1/5))⁶⁰ has 61 terms
General term T_(r+1) = ⁶⁰C_r (7^(60-r)/5) (5^(3r)/10)
∴for rational term, r = 0, 10, 20, 30, 40, 50, 60
⇒ no of rational terms = 7
∴ number of irrational terms = 61 - 7 = 54