由均值不等式ab/c+bc/a>=2根号(ab/c*bc/a)=2bbc/a+ca/b>=2根号(bc/a*ca/b)=2cca/b+ab/c>=2根号(ca/b*ab/c)=2a若要同时取等号则ab/c=bc/a=ca/bab/c=bc/aa^2=c^2是正数,a=c同理,bc/a+ca/b则a=b所以a=b=c和a,b,c是不全...