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Question: Answered & Verified by Expert
Let a=i^+j^+k^ and b=j^-k^. If c is a vector such that a×c=b and a·c=3, then a·(b×c) is equal to:
MathematicsVector AlgebraJEE MainJEE Main 2021 (26 Aug Shift 1)
Options:
  • A 6
  • B -2
  • C 2
  • D -6
Solution:
2192 Upvotes Verified Answer
The correct answer is: -2

We know that, for vectors a, b and c
a·(b×c)=abc=cab

a·(b×c)=(c×a)·b

=-b·b

a×c=bc×a=-b

=-b2

=-12+-122

=-2

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