Minimization using lagrange

Hey, I am trying to solve the problem:

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A plane with equation *x**a*+*y**b*+*z**c*=1 (*a*,*b*,*c*>0)

together with the positive coordinate planes forms a tetrahedron of volume *V*=16*a**b**c*

Find the plane that minimizes *V* if the plane is constrained to pass through a point *P*=(5,2,2) .

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Using lagrange multipliers, but cannot figure it out. Anyone know how to do it?

x/9 + y/9 + z/9 = 1 is incorrect