Find the projection of vector -i+2j-3k along . . .

Question : Find the projection of vector -i+2j-3k along the vector 2i+j-2k.

Doubt by Suhani

Solution : 

Let
A = -i+2j-3k
B = 2i+j-2k

We know, 

The scalar projection of A on B is given by 
=A.B/B

=[(-i+2j-3k).(2i+j-2k)]/|2i+j-2k|
=[(-1)(2)+(2)(1)+(-3)(-2)]/[√(2)²+(1)²+(-2)²]
=[-2+2+6]/√[4+1+4]
=[6]/√9
=6/3

=2