If →a=2^i−^j+^k,→b=^i+^j−2^k and →c=^i+3^j−(λ2+3λ)^k, where λ is a constant and →a is perpendicular to →c−λ→b, then sum of the different values of λ is
A
−1
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B
1
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C
2
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D
−2
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Solution
The correct option is A−1 Given : →a=2^i−^j+^k,→b=^i+^j−2^k and →c=^i+3^j−(λ2+3λ)^k
As, →a is perpendicular to →c−λ→b, then →a⋅(→c−λ→b)=0⇒→a⋅→c−λ→a⋅→b=0⇒2−3−(λ2+3λ)−λ(2−1−2)=0⇒λ2+2λ+1=0⇒(λ+1)2=0∴λ=−1