# Find the Equation of the Plane Through the Line of Intersection of the Planes X + Y + Z = 1 and 2x + 3y + 4z = 5 Which is Perpendicular to the Plane X − Y + Z = 0. Also Find the Distance of the Plane, Obtained Above, from the Origi - Mathematics

Find the equation of the plane through the line of intersection of the planes x + y + z = 1 and 2x + 3y + 4z = 5 which is perpendicular to the plane x − y + z = 0. Also find the distance of the plane, obtained above, from the origin.

#### Solution

Equation of the plane through the line of intersection of the two planes is

 (x+y+z−1)+λ(2x+3y+4z−5)=0⇒(1+2λ)x+(1+3λ)y+(1+4λ)z−1−5λ=0                        .........(1)

Normal vector of the required plane is

vecN =(1+2λ)hati+(1+3λ)hatj+(1+4λ)hatk

Since this plane is perpendicular to x-y+z=0, their normals are also perpendicular.

⇒vecN_1.vecN_2=0

⇒((1+2λ)hati+(1+3λ)hatj+(1+4λ)hatk).(hati−hatj+hatk)=0

⇒1+2λ−1−3λ+1+4λ=0

⇒λ=−1/3

Substituting the value of λ in equation (1), to obtain the required equation of the plane

(1+2(−1/3))x+(1+3(−1/3))y+(1+4(−1/3))z−1−5(−1/3)

=0

xz+2=0

To find out the distance of this plane from the origin we need to convert this equation to the standard form:

lx+my+nz=d

Dividing both sides of the equation by
sqrt2

, we get:

x/sqrt2−z/sqrt2=−2/sqrt2

x/sqrt2−z/sqrt2=−sqrt2

Hence, the distance of the plane from the origin is
sqrt2  units.

Concept: Distance of a Point from a Plane
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#### APPEARS IN

NCERT Class 12 Maths
Chapter 11 Three Dimensional Geometry
Q 11 | Page 493