Question

If two vectors $2 \hat { i } + 3 \hat { j } - \hat { k }$ and $- 4 \hat { i } - 6 \hat { j } - \lambda \hat { k }$ are parallel to each other then value of λ be

• A. 25
• B. 26
• C. – 26
• D. – 25

Answer 1

Answer: (C)

– 26

Answer 2

If $\vec { A }$ and $\vec { B }$ are perpendicular to each other then $\vec { A } \cdot \vec { B } = 0$ $\Rightarrow a _ { 1 } b _ { 1 } + a _ { 2 } b _ { 2 } + a _ { 3 } b _ { 3 } = 0$

So, $\Rightarrow \lambda = - 26$