CUET · MATHS · PYQ PAPER 2025
If \( \vec{a}\) is a unit vector and \((\vec{x}-\vec{a}) \cdot(\vec{x}+\vec{a})=15\), then the value of \(|\vec{x}|\) is :
- A 0
- B 16
- C 4
- D 2
Answer & Solution
Correct Answer
(C) 4
Step-by-step Solution
Detailed explanation
\((\vec{x}-\vec{a}) \cdot(\vec{x}+\vec{a})=15\) \(|\vec{x}|^2 - |\vec{a}|^2 = 15\) \(|\vec{x}|^2 - 1^2 = 15\) \(|\vec{x}|^2 = 16\) \(|\vec{x}| = 4\)
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