MCQ
The points $A\,(a),\,B\,(b),\,C\,(c)$ will be collinear if
  • A
    $a + b + c = 0$
  • $a \times b + b \times c + c \times a = 0$
  • C
    $a\,.\,b + b\,.\,c + c\,.\,a = 0$
  • D
    None of these

Answer

Correct option: B.
$a \times b + b \times c + c \times a = 0$
b
(b) $(b - a) \times (c - b) = 0$ or $b \times c + a \times b + c \times a = 0$.

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