Q.

Let the system of linear equations

-x+2y-9z=7

-x+3y+7z=9

-2x+y+5z=8

-3x+y+13z=λ

has a unique solution x=α,y=β,z=γ. Then the distance of the point (α,β,γ) from the plane 2x-2y+z=λ is           [2023]

1 9  
2 7  
3 13  
4 11  

Ans.

(2)

We have, -x+2y-9z=7  ... (i)

-x+3y+7z=9  ... (ii)

-2x+y+5z=8  ... (iii)

-3x+y+13z=λ  ... (iv)

From (i), we have x=2y-9z-7  ... (v)

Substituting the value of x in (ii) and (iii), we get

y+16z=2 and -3y+23z=-6

Solving these two equations, we get y=2,z=0.

x=2×2-9×0-7=4-7=-3  [Using (v)]

Now, substituting the value of x,y,z in equation (iv), we get

-3×(-3)+2+13×(0)=λλ=11

Distance of (-3,2,0) from the plane 2x-2y+z=11 is

d=|-6-4-114+4+1|=213=7 units.