Question:hard

If for some \(m\in R\) the lines \(L_1:\frac{x+1}{m} = \frac{y-m}{-1} = \frac{z-1}{1}\) and \(L_2:\frac{x+2}{-4} = \frac{y+1}{9} = \frac{z+1}{1}\) are coplanar, then line \(L_1\) passes through the point

Show Hint

Use the coplanarity determinant to find \(m\), then test which point lies on \(L_1\).
Updated On: Oct 1, 2026
  • \((-7,2,-5)\)
  • \((7,-2,5)\)
  • \((7,2,5)\)
  • \((7,-2,-5)\)
Show Solution

The Correct Option is B

Solution and Explanation

Step 1: Parametrise L1 for m = 2
Points on $L_1$: $(-1+2t,\ 2-t,\ 1+t)$.

Step 2: Find the point
Set $t=4$: $(7,-2,5)$, option (B). This uses $m=2$, one of the two values that make the lines coplanar.

Final Answer:
Point $(7,-2,5)$ lies on $L_1$ for $m=2$, option (B). \[ \boxed{(7,-2,5)} \]
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