Arrived in the seventh middle school.

The first and second classes in the morning were math classes, and the math teacher was still the sick old teacher, who spoke like a woman. The students sitting in the back row could barely hear it. However, Wang Tian's personal level has now reached level 15, and the increase in his muscles and bones attributes has improved his own abilities a lot, and he can barely hear it when he is sitting in the back row.

Leng Xinxin next to her took out her mobile phone to play cool running as soon as she started class, and the math teacher didn't care about her at all. What he thought in his heart was that he was going to retire anyway, and it didn't matter if the students listened or not, as long as he lectured on it, he would complete the task.

But it doesn't matter if she listens to the class coldly or not, anyway, her father is the president of the group company, and when she reaches a certain age, she can go to work directly in the company, and she is not an ordinary employee. Even if she says she wants to go now, I'm afraid Leng Qian will arrange a good position for her.

Wang Tian listened carefully, he used to give up studying for money, but now he doesn't need it. Now the money in his package is unlimited, and it stands to reason that it doesn't matter if he doesn't study. But he still has to study seriously, first, because he thinks this opportunity is rare. Second, he believes that learning knowledge is his own business, and learning is not for further education, but for improving personal quality. People who are knowledgeable are better than others in every aspect.

These two lessons are about mean inequalities: Hn≤Gn≤An≤Qn. That is, the harmonic mean does not exceed the geometric mean, and the geometric mean does not exceed the arithmetic mean.

1. Harmonic mean: Hn=n/(1/a1+1/a2++1/an)2, geometric mean: Gn=(a1a2an)^(1/n)3, arithmetic mean: An=(a1+a2++an)/n4, square mean: Qn=√[(a1^2+a2^2++an^2)/n] These four averages satisfy Hn≤Gn≤An≤Qn, where a1, a2、...、an∈R+, if and only if a1=a2=...=an, take "=" Number.

Then the math teacher talked about the various deformations of mean inequality, and the sophomore mathematics basically has the following three deformations: (1) For the real numbers a, b, there are a^2+b^2≥2ab (take the "=" sign if and only if a=b).

(2) For the non-negative real numbers a,b, there are a+b≥2√(a*b)≥0, that is, (a+b)/2≥√(a*b)≥0.

(3) For negative real numbers a, b, there is a+b