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If a⃗=i^−j^+k^\vec{a} = \hat{i} - \hat{j} + \hat{k}, b⃗=2i^+j^−3k^\vec{b} = 2\hat{i} + \hat{j} - 3\hat{k}, c⃗=2i^−j^+7k^\vec{c} = 2\hat{i} - \hat{j} + 7\hat{k} and a⃗×(b⃗×c⃗)=λb⃗+μc⃗\vec{a} \times (\vec{b} \times \vec{c}) = \lambda \vec{b} + \mu \vec{c}

(When λ\lambda, μ\mu are scalars), then the value of λ+μ\lambda + \mu is:

Solution

✅ Correct Option: 2

Using identity a⃗×(b⃗×c⃗)=(a⃗⋅c⃗)b⃗−(a⃗⋅b⃗)c⃗\vec{a} \times (\vec{b} \times \vec{c}) = (\vec{a} \cdot \vec{c})\vec{b} - (\vec{a} \cdot \vec{b})\vec{c}. a⃗⋅c⃗=2+1+7=10\vec{a} \cdot \vec{c} = 2 + 1 + 7 = 10. a⃗⋅b⃗=2−1−3=−2\vec{a} \cdot \vec{b} = 2 - 1 - 3 = -2. So expression =10b⃗+2c⃗= 10\vec{b} + 2\vec{c}. Hence λ+μ=10+2=12\lambda + \mu = 10 + 2 = 12.

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