Đặt \(x = \frac{1}{a} , y = \frac{1}{b} , z = \frac{1}{c} \Rightarrow x + y + z = 1\)

Ta có:

\(\text{VT} = \frac{1}{2} \left(\right. x + y + z + \frac{1}{y z} + \frac{1}{z x} + \frac{1}{x y} \left.\right) = \frac{1}{2} \left(\right. 1 + \frac{x + y + z}{x y z} \left.\right) = \frac{1}{2} \left(\right. 1 + \frac{1}{x y z} \left.\right)\) \(\text{VP} = \sqrt{\frac{1 / x y z}{\left(\right. 1 / x + 1 / y z \left.\right) \left(\right. 1 / y + 1 / z x \left.\right) \left(\right. 1 / z + 1 / x y \left.\right)}} = \frac{1}{2} \left(\right. 1 + \frac{1}{x y z} \left.\right)\)

⇒ Đẳng thức đúng

quy luật: hiệu kế tiếp bằng hiệu trước nhân 2 trừ 1.

Đáp án: \(70\) và \(135\).

Tet, or Lunar New Year, is the most important festival in my hometown. It usually takes place in late January or early February. Before Tet, people clean and decorate their houses with peach blossoms and kumquat trees. On the first day of the New Year, families gather together, share special meals like sticky rice cakes, and give lucky money to children. Traditional customs such as visiting relatives, making offerings to ancestors, and attending local festivals make Tet a warm and meaningful celebration. Everyone feels hopeful for a prosperous year ahead.