Q60 / 90 · JEE Main 2021 (27 Aug Shift 1) · Mathematics

If 0<x<1, then 32x2+53x3+74x4+…, is equal to

  • Correct answer
    A
    xx+11-x+loge1-x
  • B
    x1-x1+x+loge1-x
  • C
    1+x1-x+loge1-x
  • D
    1-x1+x+loge1-x

Solution

32x2+53x3+74x4+---

⇒1+12x2+1+23x3+1+34x4+----

⇒x2+x3+x4---+12x2+23x3+34x4---

⇒x2+x3+x4---+1-12x2+1-13x3--

⇒2x2+x3+---+-12x2-x33--

S⇒2x21-x+ln1-x+x

=2x2+x-x21-x+ln 1-x

=x2+x1-x+ln1-x

=xx+11-x+ln1-x

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

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