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CUET · MATHS · PYQ PAPER 2025

If \(\vec{a}, \vec{b}\) and \(\vec{c}\) are three unit vectors such that \(\vec{a}+2 \vec{b}-3 \vec{c}=\overrightarrow{0}\), then the value of \(2 \vec{a} \cdot \vec{b}-6 \vec{b} \cdot \vec{c}-3 \vec{c} \cdot \vec{a}\) is

  1. A \(-7\)
  2. B \(-14\)
  3. C 7
  4. D 14
Verified Solution

Answer & Solution

Correct Answer

(A) \(-7\)

Step-by-step Solution

Detailed explanation

\(( \vec{a}+2 \vec{b} )^2=(3 \vec{c})^2 \Rightarrow \vec{a}^2+4 \vec{b}^2+4 \vec{a} \cdot \vec{b}=9 \vec{c}^2\) \(1+4(1)+4 \vec{a} \cdot \vec{b}=9(1) \Rightarrow 4 \vec{a} \cdot \vec{b}=4 \Rightarrow \vec{a} \cdot \vec{b}=1\)…
From CUET
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