MCQ
Number of irrational terms in the expansion of $\Big(5^{\frac{1}{6}}+2^{\frac{1}{8}}\Big)^{100}$ is:
  • A
    96
  • 97
  • C
    98
  • D
    99

Answer

Correct option: B.
97
$\text{T}_{\text{r}+1}​=^{100}\text{C}_\text{r}​5^{\frac{(\text{r}-100)}{6}}2^{\frac{\text{r}}{8}}$
Hence we get rational terms when
r = 8k where k is an integer and $\frac{8\text{k}-100}{6}$ is an integer
r = 16, 40, 64, 88
Hence we get in total 4 rational terms.
However, total number of terms will be 101
Hence total number of irrational terms is 101 - 4
= 97 terms.

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