ab/a+b=1/3 ,(a+b)/ab=3 1/a+1/b=3bc/b+c=1/4 ,(b+c)/bc=4 1/b+1/c=4ca/c+a=1/5 ,(a+c)/ac=5 1/a+1/c=51/a+1/b+1/c=6bc/abc+ac/abc+ab/abc=6(ab+bc+ac)/abc=6则 abc/(ab+bc+ac) =1/6x/x²-x+1=7x²-x+1/x=1/...