alleryA line with direction ratios $(k,2,3)$ is perpendicular to a line with direction ratios $(1,-2,1)$. Then $k$ equals:
A4
B1
C7
D$-1$
Answer & Solution
Correct answer: B. 1
Perpendicular ⟹ k·1+2·(−2)+3·1 = 0 ⟹ k−4+3=0 ⟹ k=1.
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