If a variable plane forms a tetrahedron of constant volume 64k3 with the co-ordinate planes, then the locus of the centroid of the tetrahedron is
xyz=6k3
Let the variable plane intersect the co-ordinate axes at A(a, 0, 0), B(0,b, 0) and C(0, 0, c). Then the equation of the plane will be
xa+yb+zc=1 ......................(i)
Let P (α,β,γ) be the centroid of tetrahedron OABC. Then,
α=a4,β=b4,γ=c4 or a=4α, b=4β, c=4γ.⇒Volume of tetrahedron=13×(Area ofΔAOB)×OC⇒64k3=13(12ab) c=abc6⇒64k3=(4α)(4β)(4γ)6⇒k3=αβγ6
Therefore, the required locus of the centroid P is xyz=6k3