Q83 / 125 · BITSAT 2017 · Mathematics

If ∫(x)5dx(x)7+x6=λlogx9x9+1+C, then a+λ equal to

  • A
    2
  • Correct answer
    B
    >2
  • C
    <2
  • D
    >3

Solution

Let I=∫dxx2+x7

=∫dxx71(x)5+1

Put 1+1x5=t

⇒ -52·1(x)7dx=dt

∴ I=-25∫dtt=-25logt+C

=-25log1+1x5+C

=-25logx5/2+1x5/2+C

⇒ λ=-25 and a=52

∴ a+λ=2.1>2

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

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