huong dan cau 5 de thi vao 10 thanh pho ha noi 2013-2014

Ta co       6  1  1  1 111 6

b a c ab ca bc abc ca bc ab c b

a

c

y b

x

1

;

1

;

1

3 6

2

z y x z y x zx yz xy z y



3

2



















Do a;b;c > 0  x; y; z > 0 A 0 nen (1)  A 3





















3 3

1 1

2 2 2 2 2 2

A z y x z y x c b

Chu y: trong loi giai tren da su dung bat dang thuc

  3 ( ) )

(

3 x2 y2 z2  xyz 2  xyyzzx de nghi cac ban tu cm

GV: TRAN QUY DUONG

THCS NGUYEN TRAI -THANH XUAN