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Class 12 Three Dimensional Geometry · Assertion Reason1 Marksparallel_lines

Class 12 Maths · Three Dimensional Geometry · Assertion Reason #21

Assertion (A): The lines through (4,7,8),(2,3,4) and through (−1,−2,1),(1,2,5) are parallel. Reason (R): Vector lines with directions b₁,b₂ are parallel if b₁·b₂=0.

✅ Step-by-Step Solution

Final Answer: Option (C): A is true but R is false.
  1. Directions (−2,−4,−4) and (2,4,4) are proportional. Zero dot product instead tests orthogonality.

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