The vectors -are and coplanar if


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

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