1.
Let the system of linear equations
−x+2y+9z=7,-x + 2y + 9z = 7,

−x+3y+7z=9,-x + 3y + 7z = 9,

−2x+y+5z=8,-2x + y + 5z = 8,

−3x+y+13z=A-3x + y + 13z = A

have a unique solution x=α,y=β,z=γx = \alpha, y = \beta, z = \gamma. Then the distance of the point (α,β,γ)(\alpha, \beta, \gamma) from the plane 2x−2y+z=A2x - 2y + z = A is
Matrices and Determinants - Medium - Question