Question

The value of $λ$ for which the vectors $i+j-k$and $λi+3j+k$ are perpendicular is ?

• A. $-2$
• B. $2$
• C. $0$
• D. $-1$
• E. $1$

Answer 1

Answer: (A)

$-2$

Answer 2

Let us consider vector $a =i+j-k$and $b =λi+3j+k$

then as these are perpendicular to each other , then from the relation we know that

$a.b=0$

⇒$(i+j-k).(λi+3j+k)=0$

⇒$λ+3-1=0$

⇒$λ=-2$ (Ans)