Question

The value of lamda for which the 2 vectors
21-1 + 2k and 3i+aj + k are perpendicular is
(A) - 8
(B) 2
(C) 8
(D) 4​

Answer 1

Answer:

write proper question you have missed I cap j cap in first vector but I can tell you by another example

Explanation:

question: If vectors A=2i+2j+3k and B=3i+6k+nk are perpendicular to each other then what the value of n?

solution:Hey there,

Well that's quite simple if you know the dot product and cross product concept in vectors.When two vectors are perpendicular to each other then their dot product is always equal to 0. As per the vectors rules for dot product:

1. i.i=1

2. j.j=1

3. k.k=1

4. i.j=0

5. j.k=0

6. i.k=0

So if you remember these rules this question is quite easy to solve.What you have to do is multiply the two given vectors according to the dot products rules.

So we have, A.B=0

(2i+2j+3k).(3i+6k+nk)=0

2i.3i + 2j.0j + 3k.(6+n)k =0

6+3(6+n)=0

6+n=-2

n=-8

Therefore the value of n is -8 for the two vectors A and B to be perpendicular.

Hope it helps! :)