The vectors - are and coplanar if

Question

Philoid · Accepted Answer

Given that,

Let

Now, are coplanar

if,

⇒ λ (λ²-1) -1(λ+2) +2(-1-2 λ)=0

⇒ λ³- λ –λ-2-2-4 λ=0

⇒ λ³- 6λ-4 =0

⇒ (λ+2)( λ²-2 λ-2)=0

⇒ λ = -2 and

⇒ λ = -2 and λ = 1±√3

The vectors -are and coplanar if