Please explain in words how would you do this, no solution needed -

Question

Vectors |A|=4, |B|=9, and the angle between A and B is 60°. Find 4A+2B

Answer 1

I assume you mean to find |4A+2B|
A•B = 4*9*cos60° = 18
(4A+2B)•(4A+2B) = 16A•A + 16A•B + 4B•B = |4A+2B|^2