Question

If $2 i + j - k$ and $i -4 j +\lambda k$ are perpendicular to each other, then $\lambda$ is equal to:

• A. -3
• B. -2
• C. -1
• D. 0

Answer 1

Answer: (B)

-2

Answer 2

Since, given vectors are perpendicular.
$\therefore(2 i + j - k ) \cdot( i -4 j +\lambda k )=0$
$\Rightarrow 2-4-\lambda=0$
$\Rightarrow \lambda=-2$