Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Vectors

Question:

If $\vec a,\vec b,\vec c$ are non-coplanar vectors and λ is a real number, then $[λ(\vec a+\vec b),λ^2\vec b,λ\vec c]=[\vec a,\vec b+\vec c,\vec b]$ for.

Options:

No value of λ

Exactly one value of λ

Exactly two values of λ

Exactly three values of λ

Correct Answer:

No value of λ

Explanation:

L.H.S. $[λ(\vec a+\vec b)×λ^2\vec b].λ\vec c=λ^4[(\vec a+\vec b)×\vec b].\vec c=λ^4[\vec a\,\vec b\,\vec c]$

R.H.S:=$\vec a×(\vec b+\vec c)]\vec b=[\vec a\,\vec c\,\vec b]=-[\vec a\,\vec b\,\vec c]$

$⇒λ^4[\vec a\,\vec b\,\vec c]=-[\vec a\,\vec b\,\vec c]$

$⇒λ^4=-1$

which is not possible