Q161 / 270 · NDA 2022 (Phase 1) · Mathematics

How many terms are there in the expansion of $\left(1+\frac{2}{x}\right)^9\left(1-\frac{2}{x}\right)^9$ ?

  • A
    9
  • Correct answer
    B
    10
  • C
    19
  • D
    20

Solution

$\left(1+\frac{2}{x}\right)^9\left(1-\frac{2}{x}\right)^9=\left(1-\frac{4}{x^2}\right)^9$ Number of terms $=9+1=10$

Hence, the correct answer is option: 'B'.

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