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📐 Mathematics  ·  Vector Algebra  ·  JEE

If a = i + 2j + 3k, then |a|<sup>2</sup> =

Answer: 14.

  • A 6
  • B 36
  • C 12
  • D 14

Correct answer: D. 14

Explanation: |a|<sup>2</sup> = 1<sup>2</sup> + 2<sup>2</sup> + 3<sup>2</sup> = 1 + 4 + 9 = 14.

xya (4,1)b (2,3)a + b (6,4)

Triangle law of vector addition: placing vector b at the head of vector a, the diagonal from the start to the final head gives the resultant a + b.

Concept context

Vectors, dot product, cross product, and geometric applications

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