Câu hỏi 71
Cho $a,b,c$ là các số thực dương. Chứng minh rằng
$$8(a+b+c)\left(\frac1a+\frac1b+\frac1c\right)\le9\left(1+\frac ab\right)\left(1+\frac bc\right)\left(1+\frac ca\right).$$
$$8(a+b+c)\left(\frac1a+\frac1b+\frac1c\right)\le9\left(1+\frac ab\right)\left(1+\frac bc\right)\left(1+\frac ca\right).$$