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CUET · MATHS · PYQ PAPER 2023

If \(|\vec{a}|=3\) and \(|\vec{b}|=4\), then a value of \(\lambda\) for which \(\vec{a}+\lambda \vec{b}\) and \(\vec{a}-\lambda \vec{b}\) are perpendicular is :

  1. A \(\frac{9}{16}\)
  2. B \(\frac{3}{4}\)
  3. C \(\frac{3}{2}\)
  4. D \(\frac{4}{3}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{3}{4}\)

Step-by-step Solution

Detailed explanation

\((\vec{a}+\lambda \vec{b}) \cdot (\vec{a}-\lambda \vec{b}) = 0\) \(|\vec{a}|^2 - \lambda^2 |\vec{b}|^2 = 0\) \((3)^2 - \lambda^2 (4)^2 = 0\) \(9 - 16\lambda^2 = 0\) \(16\lambda^2 = 9\) \(\lambda^2 = \frac{9}{16}\) \(\lambda = \frac{3}{4}\)
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