Question

1,a.b属于R+,求证a(b方+c方)+b(c方+a方)大于等于4abc

Answer 1

1.左边>=a*2bc+b*2ac=2abc+2abc=4abc

2.即√6+√7>√8+√5

即√6-√5>√8-√7

即(6-5)/(√6+√5)>(8-7)/(√8+√7)

即1/(√6+√5)>1/(√8+√7)

即√8+√7>√6+√5,显然成立