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Question

For the next two (02) items that follow :
A line L passing through the point (-1, 2, -3) is perpendicular to the plane P given by $2x + 3y + z + 5 = 0$.

What are the direction ratios of a line M parallel to the plane P ?

This question was previously asked in
NDA 1 2026 GAT Question Paper (12-Apr-2026)
The correct answer is
$< 2, 2, -10 >$

The problem asks for the direction ratios of a line M that is parallel to a given plane P.

Plane P Analysis

The equation of the plane P is given as: 2 x + 3 y + z + 5 = 0 $ The normal vector n$ to the plane P is determined by the coefficients of x, y, and z.

Normal vector n = <2, 3, 1>

Line M Condition

A line M is parallel to the plane P if its direction vector m$ is perpendicular to the plane's normal vector n.

The condition for perpendicularity is that their dot product is zero:

m · n = 0 $

Let the direction ratios of line M be <l,m,n>$. Then, the condition becomes:

< l , m , n > · < 2 , 3 , 1 > = 0 $

Or, 2l+3m+n=0$

Checking Options

We test each option's direction ratios <l,m,n>$ using the condition 2l+3m+n=0$:

  • Option 1: <-3,2,1>$
    2 ( - 3 ) + 3 ( 2 ) + 1 = - 6 + 6 + 1 = 1 0 $
  • Option 2: <3,2,-6>$
    2 ( 3 ) + 3 ( 2 ) + ( - 6 ) = 6 + 6 - 6 = 6 0 $
  • Option 3: <1,3,2>$
    2 ( 1 ) + 3 ( 3 ) + 2 = 2 + 9 + 2 = 13 0 $
  • Option 4: <2,2,-10>$
    2 ( 2 ) + 3 ( 2 ) + ( - 10 ) = 4 + 6 - 10 = 10 - 10 = 0 $

Option 4 satisfies the condition m · n = 0

Conclusion

The direction ratios <2,2,-10>$ correspond to a line M parallel to the plane P.

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