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Question

Direction: Consider the following for the two (02) items that follow :
Let L: $x + y + z + 4 = 0 = 2x -y-z+8$ be a line and P:$x+2y+3z + 1 = 0$ be a plane.

What is the point of intersection of L and P?

This question was previously asked in
NDA 2 2024 GAT Question Paper (01-Sep-2024)
The correct answer is
\((-4, -3, 3)\)

Finding the Intersection Point of Line L and Plane P

The problem asks for the coordinates of the point where a line L intersects a plane P.

Step 1: Define the Line L

The line L is defined by the intersection of two planes:

  • Plane 1: \(x + y + z + 4 = 0\)
  • Plane 2: \(2x - y - z + 8 = 0\)

To find the parametric equations for the line L, we can combine these two equations.

Step 2: Derive Parametric Equations for Line L

Add the two equations to eliminate \(y\) and \(z\):

\( (x + y + z + 4) + (2x - y - z + 8) = 0 \)

\( 3x + 12 = 0 \)

\( 3x = -12 \)

\( x = -4 \)

Now substitute \(x = -4\) back into the first equation (\(x + y + z + 4 = 0\)):

\( -4 + y + z + 4 = 0 \)

\( y + z = 0 \)

\( z = -y \)

Let's introduce a parameter, say \(t\), such that \(y = t\). Then, \(z = -t\).

So, the parametric equations for the line L are:

  • \(x = -4\)
  • \(y = t\)
  • \(z = -t\)

Any point on the line L can be represented as \((-4, t, -t)\) for some real number \(t\).

Step 3: Substitute Line Equations into Plane P

The equation of the plane P is:

\( x + 2y + 3z + 1 = 0 \)

To find the intersection point, we substitute the parametric equations of the line L into the equation of the plane P:

\( (-4) + 2(t) + 3(-t) + 1 = 0 \)

Step 4: Solve for the Parameter t

Simplify and solve the equation for \(t\):

\( -4 + 2t - 3t + 1 = 0 \)

\( -3 - t = 0 \)

\( t = -3 \)

Step 5: Calculate the Coordinates of the Intersection Point

Substitute the value of \(t = -3\) back into the parametric equations of the line L:

  • \(x = -4\)
  • \(y = t = -3\)
  • \(z = -t = -(-3) = 3\)

Therefore, the point of intersection of line L and plane P is \((-4, -3, 3)\).

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Similar Questions

  1. What are the direction ratios of the line?
  2. What is the equation to the straight line passing through the point \((-\sin\theta, \cos\theta)\) and perpendicular to the line \(x\cos\theta + y\sin\theta = 9\)?
  3. Two points $P$ and $Q$ lie on line $y = 2x + 3$. These two points $P$ and $Q$ are at a distance $2$ units from another point $R(1, 5)$. What are the coordinates of the points $P$ and $Q$?
  4. If two sides of a square lie on the lines $2x+y-3=0$ and $4x + 2y + 5 = 0$, then what is the area of the square in square units ?
  5. \(ABC\) is an acute angled isosceles triangle. Two equal sides \(AB\) and \(AC\) lie on the lines \(7x - y - 3 = 0\) and \(x + y - 5 = 0\). If \(\theta\) is one of the equal angles, then what is \(\cot\theta\) equal to ?
  6. A line through \((1, -1, 2)\) with direction ratios \(<3, 2, 2>\) meets the plane \(x + 2y + 3z = 18\). What is the point of intersection of line and plane?

  7. What is the value of \(\alpha\) ?
  8. What is the angle made by the line L with positive direction of y-axis ?
  9. Under what condition will the lines m2x + ny - 1 = 0 and n2x - my + 2 = 0 be perpendicular?

  10. ABC is an equilateral triangle and AD is the altitude on BC. If the coordinates of A are (1, 2) and that of D are (-2, 6), then what is the equation of BC?


Important Questions from Equation in a Line

  1. What are the direction ratios of the line?
  2. What is the equation to the straight line passing through the point \((-\sin\theta, \cos\theta)\) and perpendicular to the line \(x\cos\theta + y\sin\theta = 9\)?
  3. Two points $P$ and $Q$ lie on line $y = 2x + 3$. These two points $P$ and $Q$ are at a distance $2$ units from another point $R(1, 5)$. What are the coordinates of the points $P$ and $Q$?
  4. If two sides of a square lie on the lines $2x+y-3=0$ and $4x + 2y + 5 = 0$, then what is the area of the square in square units ?
  5. \(ABC\) is an acute angled isosceles triangle. Two equal sides \(AB\) and \(AC\) lie on the lines \(7x - y - 3 = 0\) and \(x + y - 5 = 0\). If \(\theta\) is one of the equal angles, then what is \(\cot\theta\) equal to ?
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