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CUET · MATHS · PYQ PAPER 2023

If the lines \(\frac{x+3}{k-5}=\frac{y-1}{1}=\frac{5-z}{-2 k-1}\) and \(\frac{x+2}{-1}=\frac{2-y}{-k}=\frac{z}{5}\) are perpendicular, then the value of \(k\) is

  1. A 1
  2. B -1
  3. C 2
  4. D -2
Verified Solution

Answer & Solution

Correct Answer

(B) -1

Step-by-step Solution

Detailed explanation

\( \vec{d_1} = (k-5, 1, 2k+1) \) \( \vec{d_2} = (-1, k, 5) \) \( \vec{d_1} \cdot \vec{d_2} = 0 \) \( (k-5)(-1) + (1)(k) + (2k+1)(5) = 0 \) \( -k+5 + k + 10k+5 = 0 \) \( 10k+10 = 0 \) \( 10k = -10 \) \( k = -1 \)