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Question: Answered & Verified by Expert
If X=4n-3n-1 : nN  and Y=9n-1 : nN, where N is the set of natural numbers, then XY is equal to
MathematicsSets and RelationsJEE MainJEE Main 2014 (06 Apr)
Options:
  • A X
  • B Y
  • C N
  • D Y-X
Solution:
1943 Upvotes Verified Answer
The correct answer is: Y
X=4n-3n-1:nN

4n-3n-1=3+1n-3n-1

=nC03o1n+nC1311n-1+.....+nCn3n-3n-1

=1+n3+nC232+.....+3n-3n-1

=nC232+nC333+.....+3n

=32nC2+nC331+nC432+.....+3n-2

=9k, where k is a natural number.

Y=9n-1 nN

∴  XY

∴  XY=Y

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