After being a tutor to my younger siblings, I went back to the laboratory after becoming popular

Chapter 12 Key Points of Problem Solving
Sheng Xiawan opened her notebook, took a pen to write something on it, and replied faintly, "No."

Sheng Xia Tian: ...

For the next itinerary, when Sheng Xiaqing was brushing the questions, Sheng Xiawan was busy with her own affairs while paying attention to Sheng Xiaqing's answers. When she found that Sheng Xiaqing frequently made mistakes on a question type, she flipped through the The book went to a blank space, and wrote down some important points on it with a "scrub...".

Sheng Xia, who was not assigned a study task, saw that the eldest sister really didn't intend to give him the paper, so she just closed her eyes and started to catch up on sleep.

Sheng Xiawan just gave Sheng Xia Qing a math test. Although the liberal arts class she chose for Sheng Xia Qing, the math test is also a liberal arts math test, and the type of questions will not be too difficult.

But Sheng Xiaqing is too weak in mathematics, so Sheng Xiawan plans to grasp her subject first, and other liberal arts questions that require rote memorization are easy to overcome.

Sheng Xiaqing got a headache when she saw the math papers, but she still worked hard and tried her best to do as many questions as possible. She really doesn't know how to solve some questions, and she can solve them step by step.The time to work hard on the questions always passed quickly, and an hour passed before you knew it, and the alarm clock that was set in advance in the midsummer evening rang.

Sheng Xiawan closed the notebook and looked sideways at Sheng Xiaqing. Sheng Xiaqing was still frowning and thinking about the topic. Sheng Xiawan lowered her head slightly to look at her paper. It was enough to see Sheng Xiaqing's seriousness from the draft paper next to the paper.

Sheng Xiawan asked softly, "Can you figure out the answer?"

Sheng Xiaqing shook her head helplessly, "Sister, I really tried my best."

"Well, I see, let me tell you the rest!"

In the following time, Sheng Xiawan answered Sheng Xia Qing's questions one by one.

This paper is a basic paper, and it is not very difficult. As long as you know how to solve the problem, it is easy to solve it.

It's just that Sheng Xiaqing was weak in mathematics when she was studying, and now that she has graduated for several years, she has forgotten many knowledge points, especially the knowledge points related to functions, which she has almost lost.

This is a very bad thing, because function is a main thread running through high school mathematics. It can be integrated with many knowledge contents instinctively, so it has always been one of the core contents of the compulsory examination of the college entrance examination. Of course, the mathematics questions for adults self-examination Certainly can not disturb the function.

Sheng Xia Wan patiently explained the problem to Sheng Xia Qing, "Xia Qing, look at this problem, it asks for the domain of a function.

When you solve the problem, the conditions are not considered enough when you seek the domain of the function.

You ignore the condition that the denominator is not zero, and mistakenly think that (x+1)=1 is true for any real number, so you are wrong.

Well, here are the points I listed for you that you should pay attention to when finding the domain of a function. You should memorize it, and pay attention to these points when you write questions later, and you will not make mistakes when finding the domain of a function. . "

Sheng Xiaqing took the paper that Sheng Xiawan handed over, on which were clearly written ten points for attention.

1. When it is an integer or an odd radical, the domain can take infinite values;
2. When it is an even-order radical, the radical number is not less than 0;

3. When it is a fraction, the denominator is not 0. When the denominator is an even radical, the radicand is greater than 0;

4. When it is exponential, the base is not 0 for zero exponent power or negative integer exponent power;

5. When it is formed by combining some basic functions through four arithmetic operations, its domain should be a set of independent variable values ​​that make each part meaningful, that is, find the intersection of the domain sets of each part;

6. The definition domain of the piecewise function is the union of the value sets of the independent variables on each piece;

7. For functions established by practical problems, in addition to making the analytical formula meaningful, it is also necessary to consider the requirements of the actual meaning for independent variables;
8. For functions with parameter letters, when finding the domain, it is generally necessary to classify and discuss the values ​​​​of the letters, and pay attention to the definition domain of the function is a non-empty set;
9. The true number of the logarithmic function must be greater than zero, the base must be greater than zero and not equal to 1;

10. The cutting function in the trigonometric function should pay attention to the restriction of the diagonal variable.

"Thank you big sister, I will remember them." Sheng Xiaqing thanked her sincerely.

This note is written by hand and not printed out. I think it was written by the elder sister just now. The elder sister was obviously busy with her own affairs just now, but she still took time to pay attention to her own situation and sort out the key points for herself. This reminded her, The time when the eldest sister took her at home.

When Sheng's father and Sheng's mother were absent in daily life due to work, Sheng Xiawan, the eldest sister, really took care of her younger siblings, especially Sheng Xiaqing, who was only two years younger than Sheng Xiawan, who took care of her The time is two or three years longer than the time of bringing summer.

Whether in life or studies, Sheng Xiawan took good care of her younger siblings, so before Sheng Xiawan went to college, Sheng Xiaqing's academic performance was not bad because Sheng Xiawan was tutoring her.

Everything started to become unsatisfactory when she was in her second year of high school, Sheng Xiawan was admitted to university and went to other provinces.

At that time, although Sheng Xia Wan was away from home, she would still call Sheng Xia Qing every week, but communication by phone was definitely not as good as face-to-face communication. In addition, Sheng Xia Wan was very busy, and she joined the student union as soon as she entered the university. When I was a sophomore, I even became the president of the student union. When I was busy, I couldn't take care of so much. As time passed, although I made this call, the time spent on the call became less and less.

Sheng Xiaqing was thinking that her eldest sister was busy, so don't waste her time. On the other hand, Sheng Xiawan was because she was busy, and on the other hand, she thought that Sheng Xiaqing had grown up, and she took care of so much, so she slowly let go.

However, Sheng Xiaqing happened to be in the second year of high school when she was just divided into subjects. Without a pillar around her, she couldn't adapt to anywhere, and her grades plummeted.

She didn't learn well in the second year of high school. When she was in the third year of high school, she would only understand the questions even more. Every time she took the exam, the questions knew her, but she didn't know the state of the questions.

In this state, when she was in the first semester of her third year of high school, she went to Lin City's film and television city with her classmates, but was temporarily dragged by a crew to be an extra performer.

At that time, she just acted as a passer-by, but since then she fell in love with acting, and she put less focus on her studies. She began to ask for leave frequently to go to the film and television city to wait for a chance to play tricks. She became the current manager, Sister Hua, and has since become a member of the entertainment circle. As for her college entrance examination, one can imagine what her grades will be like for a person who hasn't had much class in her third year of high school.

(End of this chapter)