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Question: Answered & Verified by Expert
If fx=x–1x–2x–3x–4x–5, then the value of  f ′ 5 is equal to
MathematicsDifferentiationJEE Main
Options:
  • A 0
  • B 120
  • C 24
  • D 5
Solution:
1842 Upvotes Verified Answer
The correct answer is: 24
f ′ x = x–2 x–3 x–4 x–5 + x−1 x−3 x−4 x−5
+......+x-1x-2x-3x-4
Putting x=5, we get,
f ′ 5 =0+0+0+0+ 5−1 5−2 5−3 5−4
f ′ 5 =24

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