MCQ
Three points whose position vectors are $a + b,\,\,a - b$ and $a + kb$ will be collinear, if the value of   $k $ is
  • A
    Zero
  • B
    Only negative real number
  • C
    Only positive real number
  • Every real number

Answer

Correct option: D.
Every real number
d
(d) $\overrightarrow {AB} = \lambda \overrightarrow {BC} $, (for collinearity)

Here $\overrightarrow {AB} = - 2b,$ $\overrightarrow {BC} = (k + 1)b$

Hence $\forall \,\,k \in R \Rightarrow \overrightarrow {AB} = \lambda \overrightarrow {BC} .$

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