A, CHO A,B > 0, CMR

Câu 3:

a, Cho a,b > 0, CMR:

1

a

+

1

b



4

a b



b, Cho a,b,c,d > 0



CMR:

^a

^d



+

^d

^b



+

^{b c}



+

^c

^a





0

b c

c

a

d

b

a

d