Qin Ke could see the solution to the problem at just one glance, and he quickly wrote in his notebook:

"This question is not difficult. The key is to change your thinking. You see, there are two parameters a and b, and there are many constraints. It is not intuitive and seems a bit difficult to start. Here we can use the solution of 'combination of numbers and shapes'

Problem-solving strategy. Do you know this problem-solving strategy?"

"Teacher talked about it in the training." Ning Qingyun nodded, but there was still a little confusion in his eyes, as if he didn't understand how to apply it to this topic.

It is rare to see such a look on the school committee girl who is always cold and proud. She is inexplicably more fragile and cute, which makes her have a strong desire to protect her.

Girl, why do I feel like this guy is a little too cute tonight!

Qin Ke calmed down and continued to write calmly and calmly:

“Both numbers and shapes can reflect the attributes of things, and the combination of numbers and shapes can solve mathematical problems through the correspondence and transformation between numbers and shapes. Specifically, when solving problems, the problem of graphic properties can be solved with the help of quantitative relationships.

Deduction and specific quantification, or quantitative relationship problems can be intuitively visualized with the help of geometric backgrounds, and complex problems can be simplified and abstract problems can be made concrete by 'using shapes to help numbers' or 'using numbers to solve shapes'. It is most suitable for use in

On this type of topic.”

Without waiting for Ning Qingyun's answer, he directly wrote the solution to the question:

"Suppose an equation f(x)= x^2ax2b-2, from what we know, we can get f(0)>0, f(1)<0, f(2)>0, so we can get three inequalities

Got:

b>1,a2b<1,ab>-1,

Then we directly draw the area that satisfies these three inequalities in the rectangular coordinate plane aob."

Qin Ke drew a Cartesian coordinate plane and drew several straight lines.

"Look, we can see that in the area that satisfies three inequalities at the same time, the slope of the line connecting each point (a, b) and (1,4) is exactly (b-4)/(a-

1), so you can easily get the answer, (b-4)/(a-1)∈(1/2,3/2).”

"This is the problem-solving strategy of combining numbers and shapes. You only need to transform the conditions in the question into f(0)>0, f(1)<0, f(2)>0, and then transform this relatively abstract quantitative relationship into

It is an intuitive positional relationship between geometric figures, which can simplify the problem immediately."

"There are many similar question types. Let me write a few questions for you..."

Ning Qingyun stared blankly at Qin Ke, who was writing quickly and with a serious look on his face. He once again sighed from the bottom of his heart. This guy's clear thinking and quick thinking were the only ones he had ever seen in his life.

Especially his brain, which is truly a genius' brain, is more than one level higher than that of an ordinary person like himself.

He actually thought of the solution to this difficult problem that he had been pondering for more than ten minutes but had no idea of ​​the solution at a glance, and he knew that he could use the most appropriate "combination of numbers and shapes" strategy to solve the problem!

Ning Qingyun's basic foundation is extremely solid. At this time, listening to Qin Ke's detailed explanation with examples again in the notebook, he quickly mastered the key. If he encounters similar questions that require the use of "combination of numbers and shapes" in the future,

She was confident that she could convert "number" and "shape" in just ten seconds and solve the problem according to Qin Ke's idea.

Ning Qingyun couldn't help but feel lucky for her decision just now. Although she had to spend time teaching Qin Ke English, she probably learned more from this guy.

"Okay..." The girl reached out and held down Qin Ke's pen.

Qin Ke looked up unexpectedly.

Ning Qingyun wrote in the notebook: "It's too hard for you to write like this. Please explain it to me in detail next time when you can talk easily."

Qin Ke shook his wrist, which was a bit sore. He didn't expect this guy to be considerate.

"OK."

"I have English notes from the first year of high school in the dormitory. I will bring them to you tomorrow..."

"Thank you, school committee member. I love reading your school committee secrets the most! I can't wait to sleep with you in your arms."

Ning Qingyun's face turned slightly red and she said angrily: "Jing Ai is talking nonsense. I'll lend you my notebook, but you can't hold it to sleep."

Qin Ke was speechless, girl, I was joking, it was just an exaggerated rhetorical technique. I am not a pervert.

Qin Ke finally discovered that this guy was very lacking in humor, he would take every joke seriously, and he was very easy to laugh at. He didn't know if no one had teased her before or she was born with a low point of laughter.

Ning Qingyun wrote again: "Oh, by the way, Teacher Zheng said at the end of the math class that we will not come to the classroom for self-study tomorrow. We will go to the mathematics laboratory in Building B to participate in the Mathematical Olympiad training class. You

Remember?"

"Remember."

"The training for the Mathematical Olympiad will still start at eight in the morning. Don't be late."

Qin Ke made an OK gesture and looked at his notebook. He actually had two full pages filled with conversations between himself and Ning Qingyun.

He couldn't help but have some feelings. When he first sat at the same table with this guy, he probably never dreamed that he would "talk" to her like this in class for two pages, right?

"By the way, School Committee, is the little note you gave me in the evening still there?"

"I haven't had time to throw it away yet. What's wrong?"

Ning Qingyun hesitated for a moment, then took out the crumpled piece of paper from her schoolbag.

"Can you give it to me?"

"What are you doing here?"

Qin Ke didn't answer, but stretched out his hand and snatched it from her hand.

"Hey, you guy...can you stop robbing me all the time? You were a robber in your last life!" Ning Qingyun felt that Qin Ke's fingers had accidentally slipped across her little hand, and her face suddenly turned a little red, embarrassed.

He glared at Qin Ke in annoyance.

"You have discovered all this, and I also feel that I am quite suitable to be a robber." Qin Ke carefully flattened the small piece of paper, tucked it into the book, and then smiled and replied with a white tooth, and wrote in regular handwriting:

"I plan to use this note as motivation to motivate myself to study hard. I will read it every day, keep it in my heart, and treasure it for a lifetime."

Ning Qingyun's heartbeat was inexplicably chaotic. She brushed the hair on her temples, covered her little ears that were a little hot for some reason, reached out to take back her Mathematical Olympiad exercise book, and then wrote cutely in her notebook.

Said: "You are boring, study hard! Memorize all the English words in the textbook first!"

"Understood." Qin Ke actually just wanted to write the first sentence "as a motivation to spur myself to study hard" to please Ning Qingyun, but after seeing her cute and embarrassed expression, he somehow added the next three sentences by mistake.

.

At this time, he also felt a little regretful. If he really annoyed this tender-skinned school committee member, it would be really self-defeating.

Fortunately, Ning Qingyun didn't explode now. Qin Ke quickly pretended to study seriously and took out the English textbook to memorize the words.

Seeing his good-natured appearance, Ning Qingyun couldn't help but raise the corner of her mouth again. She ignored Qin Ke and took the "dialogue book" placed in the middle of the table, and read Qin Ke's explanation carefully again.

The question process and subsequent examples are explained.
Chapter completed!