Q.

The vector 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 is:

1 r→×(i^+k^)+2=0  
2 r→·(i^-k^)-2=0  
3 r→·(i^-k^)+2=0  
4 r→×(i^-k^)+2=0  

Ans.

(3)

Let the plane be   (x+y+z-1)+λ(2x+3y+4z-5)=0

⇒(2λ+1)x+(3λ+1)y+(4λ+1)z-(5λ+1)=0

⊥ to the plane   x-y+z=0

⇒λ=-13

⇒the required plane is x-z+2=0