Question

two vectors P=2i+bj+2k and Q=i+j+k will be parallel find value of b??​

Answer 1

Given that,

Vector P = 2i+bj+2k

Vector Q = i+j+k

To find,

The value of b if vectors P and Q are parallel to each other.

Solution,

If two vectors are parallel to each other, then their dot product is maximum i.e. 1. So,

$P{\cdot}Q=1\\\\(2i+bj+2k){\cdot} (i+j+k)=1\\\\2+b+2=1\\\\b=-3$

So, the value of b is equal to -3.

Answer 2

Answer:

b=2

Explanation:

Given :

P=2i+bj+2k

Q=i+j+k

P & Q are parallel

Solution :

Since, P and Q are parallel

Therefore, their direction ratio will be equal

$\frac{2}{1}=\frac{b}{1} =\frac{2}{1}$

b=2