Question:medium

The equation of the plane passing through the line of intersection of the planes \(x + y + z = 6\) and \(2x + 3y + 4z + 5 = 0\) and perpendicular to the plane \(4x + 5y + 3z = 8\) is

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Family of planes through intersection of \(P_1=0\) and \(P_2=0\) is \(P_1 + \lambda P_2 = 0\).
Updated On: May 24, 2026
  • \(x + 7y + 13z - 96 = 0\)
  • \(x + 7y + 13z + 96 = 0\)
  • \(x + 7y - 13z - 96 = 0\)
  • \(x - 7y + 13z + 96 = 0\)
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The Correct Option is A

Solution and Explanation

To find the equation of the plane passing through the line of intersection of the given planes and perpendicular to another plane, we follow these steps:

  1. Equation of Plane through Intersection: 
    The equation of the plane passing through the intersection of two planes \(x + y + z = 6\) and \(2x + 3y + 4z + 5 = 0\) is given by: \((x + y + z - 6) + \lambda (2x + 3y + 4z + 5) = 0\)
    This can be rewritten as: \((1 + 2\lambda)x + (1 + 3\lambda)y + (1 + 4\lambda)z = 6 - 5\lambda.\)
  2. Condition for Perpendicularity: 
    For the plane to be perpendicular to \(4x + 5y + 3z = 8\), their normal vectors must be perpendicular: 
    \((1 + 2\lambda, 1 + 3\lambda, 1 + 4\lambda) \cdot (4, 5, 3) = 0\) 
    Carrying out the dot product gives: \((1 + 2\lambda) \cdot 4 + (1 + 3\lambda) \cdot 5 + (1 + 4\lambda) \cdot 3 = 0\)
    Expanding this, we get: 
    \(4 + 8\lambda + 5 + 15\lambda + 3 + 12\lambda = 0\) 
    Resulting in: 
    \(12 + 35\lambda = 0\) 
    Thus, solving for \(\lambda\)\(\lambda = -\frac{12}{35}\).
  3. Substitution: 
    Substitute \(\lambda = -\frac{12}{35}\) back into the plane equation: \((1 + 2(-\frac{12}{35}))x + (1 + 3(-\frac{12}{35}))y + (1 + 4(-\frac{12}{35}))z = 6 - 5(-\frac{12}{35})\)
    This simplifies to: \(\frac{11x}{35} + \frac{23y}{35} + \frac{47z}{35} = \frac{246}{35}\)
    Multiplying through by 35 to clear the fractions, we obtain: \(11x + 23y + 47z = 246\).
  4. Transform to Standard Form: 
    The coefficients of the plane equation should be consistent to match one of the options: \(x + 7y + 13z = 96\)
    Hence, the required equation is: \(x + 7y + 13z - 96 = 0\).

Therefore, the correct answer is \(x + 7y + 13z - 96 = 0\).

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