Question

The vectors 31-21 +k and 21 +61 +ck are perpendicular when
A
C= 6
B
c=2
C
C=-1
D
C=0
what will be the value of C?​

Answer 1

Answer:

Let

A

=2

i

^

+3

j

^

−4

k

^

and

B

=a

i

^

+b

j

^

+c

k

^

Given

A

and

B

are at right angles.

⇒

A

⋅

B

=0

⇒2a+3b−4c=0

Only option B, satisfies the above relation.

i.e a=4,b=4,c=5

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