If →a1 and →a2 are two non collinear unit vectors inclided at 60∘ to each other then the value of (→a1 - →a2) .(→2a1 + →a2 ) is
2
|→a1| = |→a2| = 1
So (→a1 - →a2) . (→2a1 and →a2) = 2 a12 - a22 - a1 a2 cos θ =12