Question

Tìm GTNN

A=x+y+\(\frac{1}{x}+\frac{1}{y}\)biet x+y=3

 

Answer 1

sai đề :v

Answer 2

Ko sai dau ban

Answer 3

sai,chưa có điều kiện của x,y

Answer 4

x, y dương nhé

Answer 5

Áp dụng BĐT \(\frac{1}{a}+\frac{1}{b}\ge\frac{4}{a+b}\):

\(x+y+\frac{1}{x}+\frac{1}{y}=3+\frac{1}{x}+\frac{1}{y}\ge3+\frac{4}{x+y}=3+\frac{4}{3}=\frac{13}{3}\)

Nên GTNN của A là \(\frac{13}{3}\) đạt được khi \(x=y=\frac{3}{2}\)

Answer 6

he he he he he he he he he che he he he he he he he he he he he he he he he  he he he he he he he he he he he he he he he he he he   he he he he he he he he