Áp dụng BĐT Cauchy cho 2 số không âm, ta có:

\(\dfrac{a^2}{b}+b\ge2\sqrt{\dfrac{a^2}{b}.b}=2a\)

\(\dfrac{b^2}{c}+c\ge2\sqrt{\dfrac{b^2}{c}.c}=2b\)

\(\dfrac{c^2}{a}+a\ge2\sqrt{\dfrac{c^2}{a}.a}=2c\)

Cộng từng vế BĐT ta được:

\(\dfrac{a^2}{b}+\dfrac{b^2}{c}+\dfrac{c^2}{a}+b+a+c\ge2a+2b+2c\)

\(\Leftrightarrow\dfrac{a^2}{b}+\dfrac{b^2}{c}+\dfrac{c^2}{a}\ge a+b+c\)

=> ĐPCM

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in  the following questions.

I did not arrive in time. I was not able to see her off.

A. She had left because I was not on time.

B. I was not early enough to see her off.

C. I arrived very late to say goodbye to her.

D. I did not go there, so I could not see her off.

Các bạn ơi cho mik hỏi các chữ số lẻ 2 là gì vậy?