1. ## Algebraic Vectors 2

Given a and b unit vectors, if |a+b|=sqrt3, determine (2a-5b) . (b+3a)

Just wanted to know if someone could check if I have the correct solution and answer to the q above.

-13a.b+6|a|^2-5|b|^2
=-13(0.5)+6(1)^2-5(1)^2
=-5.5

I got 0.5 above for a.b dot product like this:

|a+b|=sqrt3^2
|a+b|^2=(a+b)(a+b)
3=(a^2)+2a.b+b^2
0.5=a.b

2. Originally Posted by skeske1234
Given a and b unit vectors, if |a+b|=sqrt3, determine (2a-5b) . (b+3a)
-13a.b+6|a|^2-5|b|^2
=-13(0.5)+6(1)^2-5(1)^2
=-5.5
I got 0.5 above for a.b dot product like this:
Correct.