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Let a → and b → are two vectors such that a → = 2 ,   b → = 3 and a → ⋅ b → = 4 . If c → = 3 a → × b → - 4 b → , then c → is equal to

Correct answer

18

Step-by-step solution

c → 2 = 3 a → × b → - 4 b → 2 = 9 a → × b → 2 + 16 b → 2 - 24 a → × b → ⋅ b → ∵ a → × b → 2 = a → 2 b → 2 - a → ⋅ b → 2 = 4 × 9 - 16 = 20 and a → × b → ⋅ b → = 0 Hence, c → 2 = 9 × 20 + 16 × 9 = 324 ⇒ c → = 18

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