(a) Determine the maximum M of x+y+z where x,y and z are positive real numbers with 16xyz=(x+y)2(x+z)2.
(b) Prove the existence of infinitely many triples (x,y,z) of positive rational numbers that satisfy 16xyz=(x+y)2(x+z)2 and x+y+z=M.Proposed by Karl Czakler maximuminequalitiesthree variable inequalityrationalalgebra