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AP EAMCET · Maths · Binomial Theorem

The number of all possible values of k for which the expansion \((\sqrt{x}+\sqrt[k]{y})^{10}\) will have exactly nine irrational terms is

  1. A 3
  2. B 4
  3. C 5
  4. D 6
Verified Solution

Answer & Solution

Correct Answer

(C) 5

Step-by-step Solution

Detailed explanation

Total number of terms \(= 10+1 = 11\). Exactly nine irrational terms means exactly \(= 11-9 = 2\) rational terms. The general term is \(T_{r+1} = \binom{10}{r} (\sqrt{x})^{10-r} (\sqrt[k]{y})^r = \binom{10}{r} x^{\frac{10-r}{2}} y^{\frac{r}{k}}\). For a term to be rational,…