232.
A variable plane passes through a fixed point (a, b, c) and meets the co– ordinate axes in A, B. C. Show that the locus of the point common to the planes through A. B, C parallel to the co-ordinate planes isÂ
Let the equation of plane beÂ
          ...(1)
where OA = α, OB = β, OC = γ  ∵ plane (1) passes through (a, b, c)
                             ...(2)
The equation of plane through A (α, 0, 0) parallel to yz-plane is
x = α    ...(3)
The equation of plane through B (β, 0, 0) parallel to zx-plane is
y = β    ...(4)
The equation of plane through C ( γ, 0, 0) parallel to xy-plane is
z =γ        ...(5)
To eliminate α, β, γ, we put the values from (3). (4), (5) in (2) and get

 which is required locus.Â
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