Q17 / 118 · NTA Abhyas (JEE Main) 2020 · Mathematics · Sequences and Series

If a<1 and b<1, then the sum of the series aa+b+a2a2+b2+a3a3+b3+… is

  • A
    a1-a+ab1-ab
  • Correct answer
    B
    a21-a2+ab1-ab
  • C
    b1-b+a1-a
  • D
    b21-b2+ab1-ab

Solution

We have, a<1, b<1

∴   ab=ab<1

Now, aa+b+a2a2+b2+a3a3+b3+…

 =   a2+a4+a6+…+ab+ab2+ab3+…

= a21-a2+ab1-ab

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

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