Hey, I am trying to solve the problem:
A plane with equation xa+yb+zc=1 (a,b,c>0)
together with the positive coordinate planes forms a tetrahedron of volume V=16abc

Find the plane that minimizes V if the plane is constrained to pass through a point P=(5,2,2) .
Using lagrange multipliers, but cannot figure it out. Anyone know how to do it?

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