Vector Algebra — Class 12 Maths Solution

ncert exercise SA NCERT,Page 448,Ex.10.3,Q.No 9
Question

Find $|\vec x|$, if for a unit vector $\vec a,(\vec x - \vec a) \cdot (\vec x + \vec a) = 12$.

Step-by-step Solution

We have, $(\vec x - \vec a) \cdot (\vec x + \vec a) = 12 \Rightarrow |\vec x{|^2} - |\vec a{|^2} = 12$
$\Rightarrow |\vec x{|^2} - |\vec a{|^2} = 12 \Rightarrow |\vec x{|^2} - {(1)^2} = 12 \Rightarrow |\vec x{|^2} = 13$
Hence, $|\vec x| = \sqrt {13}$

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NCERT & Exemplar solution for CBSE Class 12 Mathematics, Vector Algebra. Curated by Sachin Sharma. Free for all students.