MCQ
lf $\text{AB}\perp\text{BC}$ then the value of $\lambda$ equal, where $A(2k, 2, 3), B(k, 1, 5), C(3 + k, 2, 1):$
  • A
    $3$
  • B
    $\frac{1}{3}$
  • $-3$
  • D
    $-\frac{1}{3}$

Answer

Correct option: C.
$-3$
The drs of $AB$ are $(k, 1, -2)$
The drs of $BC$ are $(3, 1, -4)$
Since, they are perpendicular, $\text{AB.BC} = 0$
$3k + 1 + 8 = 0$
$k = -3$

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