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Question: Answered & Verified by Expert
If the fourth term in the expansion of x+xlog2x7 is 4480, then the value of x where xN is equal to:
MathematicsBinomial TheoremJEE MainJEE Main 2021 (17 Mar Shift 1)
Options:
  • A 2
  • B 4
  • C 3
  • D 1
Solution:
2398 Upvotes Verified Answer
The correct answer is: 2

Given x+xlog2x7. 

The general term in the expansion of x+xlog2x7 is Cr7xrxlog2x7-r.

Then, T4=C37x4xlog2x3=4480

7·6·53·2·1x4+log2x=4480

x4+3log2x=128

x4+3log2x=27

Now, from the option only at x=2LHS=RHS.

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