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QJEEM21Mab286: JEE Main 2021 Mathematics - Class 11 JEEM21Mab286 Solution: The sum of all those terms which are rational numbers in the…

The sum of all those terms which are rational numbers in the

expansion of (21/3 + 31/4)12 is :

Multiple Choice Options

  • A 89
  • B 27
  • C 35
  • D 43

Step-by-Step Verified Solution

Tr+1=12Cr(21/3)r.(31/4)12−4{T_{r + 1}} = {}^{12}{C_r}{\left( {{2^{1/3}}} \right)^r}.{\left( {{3^{1/4}}} \right)^{12 - 4}}

Tr + 1 will be rational number when r = 0, 3, 6, 9, 12 & r = 0, 4, 8, 12

⇒\Rightarrow r = 0, 12

T1 + T13 = 1 ×\times 33 + 1 ×\times 24 ×\times 1

= 24 + 16 = 43

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