If vector →x satisfying →x×→a+(→x⋅→b)→c=→d is given by →x=λ→a+→a×→a×(→d×→c)(→a⋅→c)|→a|2, then the value of λ=
A
(→a⋅→b)|→a|2
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B
(→a⋅→x)|→a|2
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C
(→a⋅→c)|→a|2
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D
(→a⋅→d)|→a|2
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Solution
The correct option is B(→a⋅→x)|→a|2 Given: →x×→a+(→x⋅→b)→c=→d ⇒{→x×→a+(→x⋅→b)→c}×→c=→d×→c⇒(→x×→a)×→c+(→x⋅→b)(→c×→c)=→d×→c⇒(→x⋅→c)→a−(→a⋅→c)→x=→d×→c⇒→a×{(→x⋅→c)→a−(→a⋅→c)→x}=→a×{→d×→c}⇒−(→a⋅→c)(→a×→x)=→a×{→d×→c}⇒→x×→a=→a×(→d×→c)→a⋅→c⇒→a×(→x×→a)=→a×→a×(→d×→c)→a⋅→c⇒(→a⋅→a)→x−(→a⋅→x)→a=→a×→a×(→d×→c)→a⋅→c⇒→x=(→a⋅→x)→a|→a|2+→a×→a×(→d×→c)(→a⋅→c)|→a|2⋯(i)
Comparing (i) with →x=λ→a+→a×→a×(→d×→c)(→a⋅→c)|→a|2, ∴λ=(→a⋅→x)|→a|2