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Let u → , v → and w → are vectors such that u → + v → + w → = 0 → . If u → = 3 , v → = 4 and w → = 5 , then the value of u → . v → + v → . w → + w → . u → is

Options

  1. A- 25
  2. B- 27
  3. C28
  4. D25

Correct answer

A. - 25

Step-by-step solution

Given, u   → +   v   → + w   → = 0   → If u   → =   3 ;     v   → =   4 and w   → =   5 now u → + v → + w → 2 = 0 ⇒ u → 2 + v → 2 + w → 2 + 2 u → . v → + v → . w → + w → . u → = 0 ∴     9 + 16 + 25 + 2 u → . v → + v → . w → + w → . u → = 0 ∴   u → . v → + v &#

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