Xueba, I beg you to go and escort him quickly!

Xu Heng nodded.

Yue Pingting suddenly realized.

Xu Heng continued, "Look at the last question, if the I gene on another pair of chromosomes has an inhibitory effect on the expression of A and B genes, as long as there is I gene, regardless of whether there is A or B gene, it will appear white, and the genotype is IiAaBb individuals are mated with males and females, and the red-haired individuals in the offspring are individuals with genotype iiA_B_..."

“棕毛个体，也就是iiA_bb、iiaaB_，所占比例为(1/4)*(6/16)=6/64……”

"Then the last one was 9/64, and one was 49/64, got it?"

Yue Pingting thought for a while, then gradually nodded.

Xu Heng, "Since you know everything, let's look at this question."

Yue Pingting frowned instantly, "???"

"No! Wait a minute! Xu Heng! You are clearly giving me a biology question, why did you ask me a math question?"

Xu Heng, "I came up with a sudden idea, hurry up and do it, don't waste time."

whim?

smoothly?

Xu Heng, do you think so? ! ! !

PS: Here comes the fifth update!Kneel for all support!Four.

Chapter 222

topic:

In the plane Cartesian coordinate system xOy, set point set An={(0), (0), (1),...,(n,0)}, Bn={(2), (n, 0)}, n={(0, 0), (1, 1), (0, 2), ..., (n, 1)}, n∈N*.Let Mn=An∪Bn∪n.Take two different points randomly from the set Mn, and use a random variable X to represent the distance between them.

(1) When n=1, find the probability distribution of X;

(2) For a given positive integer n (n≥3), find the probability P (X≤n) (denoted by n).

When Yue Pingting saw this kind of question, she felt uncomfortable and afraid.

But Xu Heng still asked her this kind of question.

"Hey……"

He sighed resentfully.

Yue Pingting bit the bullet and looked at the test paper helplessly.

"so hard……"

After reading it again, Yue Pingting was at a loss.

After reading it a second time, she was still dazed.

"Xu Heng, are you sure this is not a question for the Mathematical Olympiad?"

Xu Heng, "Why, is it difficult? Let me tell you, the questions in the Mathematical Olympiad are much more difficult than this. Let me give you some hints."

Yue Pingting pricked up her ears and listened carefully.

Xu Heng "When n=1, all possible values ​​of X are 1, the root number 2,2, 5, and the root number [-], which can be obtained by combining the number of combinations with the formula of classical probability."

"After that, for the second question, you can assume that A(a,b) and B(c,d) are two points taken from Mn, because P(X≤n)=1-P(X>n), So you only need to consider the case of X>n, discuss the values ​​of b and d separately, combine the calculation formula of classical probability and the probability of opposite events, and you’re done!”

"do you understand?"

When Xu Heng spoke, he didn't lift his head.

Yue Pingting was speechless, her eyebrows almost twisted into twists.

This is said so fast, whose thinking can keep up...

Yue Pingting could only understand and began to answer the questions.

(1) When n=1, all possible values ​​of X...

……

(2) Set...

When b=d, then AB≤n, there is no way of taking X>n; when...

……

Unknowingly, Yue Pingting gradually became better.

Even after class, she was doing this problem.

After she regained consciousness and finished the topic, she realized that the next class had already started.

Looking at Xu Heng again, Xu Heng had already stopped.

Yue Pingting, "???"

"That...Xu Heng, do you think I did the right thing?"

"Huh? Don't you continue to give me questions?"

Xu Heng, "It's ready."

Out... out out out, out now?

Yue Pingting suddenly looked at the time!

its not right!

She didn't do this question for a long time, did she?

Yue Pingting looked bewildered.

Xu Heng scratched her nose, "You've almost finished a class, and if I don't finish the questions, it's really a failure."

Yue Pingting, "!!!"

She clearly remembered the math problems she did when there were only a few questions in Xu Heng's test paper.

But I didn't expect that just after she finished a question, Xu Heng's entire test paper was finished!

Yue Pingting, "!!!"

Biology is not mathematics, it takes a lot of words!

But when Xu Heng handed some A4 papers to Yue Pingting, she couldn't believe what she saw.

It's just a matter of not being able to write, but it's so fair!

"This is the legendary... print? My God! Xu Heng, how did you do it? I dare not do this set of test papers..."

Xu Heng rolled his eyes, "Stop doing this, don't think of ways to be lazy."

Yue Pingting was furious, "*%￥#￥..."

"Am I like that?"

Xu Heng ignored Yue Pingting, "Look at the math questions she answered."

correct!

Under his guidance, the question was correct.

Xu Heng deliberately told her how to solve the problem so quickly, just to let her hear it, but she didn't remember it...

In fact, Xu Heng's reminder has only one purpose, and that is to give her self-confidence!

Being able to solve this problem, Yue Pingting should be most grateful for her self-confidence and confidence.

But Yue Pingting watched Xu Heng put the question aside, she couldn't believe it, "Do you have anything to say?"

Xu Heng, "???"

Yue Pingting, "Is there nothing wrong?"

Xu Heng, "No! Stop thinking about it, and just read your questions!"

Yue Pingting was still a little uneasy.

"This……!"

"Forehead……"

Fine!

Yue Pingting took a deep breath and looked at her biology test paper!

Xu Heng specially prepared the biology test paper for her.

After browsing it roughly, it is the same as a normal exam paper, with single-choice questions, multiple-choice questions, and non-choice questions.

The topic is complete.

Yue Pingting couldn't help sighing again, "Hiss...! God! Xu Heng, how did you write so many words!"

Xu Heng rolled his eyes, "Do your problem!"

Yue Pingting curled her lips and began to answer the question.

Xu Heng glanced at the phone.

"One hour, you hurry up and do it quickly, I will play two games, and then I will collect the paper."

Not negotiable!

Yue Pingting was so scared that she hurried to do the questions.

Xu Heng opened the king slowly.

The game has been updated recently, saying that there are new heroes.

After Xu Heng went up to try it out, he felt that it was all right, so he went to play a simulated battle, that is, auto chess.

First game, second game, second game, first game...

Before I knew it, an hour passed.

Xu Heng closed the scroll.

Yue Pingting, "Wait a minute, it's not finished yet..."

Where did Xu Heng give her a chance, check directly.

"The multiple-choice question is wrong, look at the question."

"The little lotus just showed its sharp horns, and dragonflies stood on its head a long time ago." "Struggle to cross, fight to cross, startled a pool of gulls and herons"... These verses describe the vivid scenery of the lotus pond.Which of the following statements is correct ( )

A. The animals, plants and microorganisms in the lotus pond together form a complete ecosystem

B. Using the five-point sampling method can accurately investigate the number of species of Odonata in the lotus pond

C. Emerging lotus, floating water lily and submerged aquatic plants reflect the vertical structure of the community

D. The main factors affecting the distribution of birds such as "gulls" in lotus ponds are light and human activities

Xu Heng, "The test here is the structure of the ecosystem. What are the components of the ecosystem?"

Yue Pingting, "Producers, consumers, decomposers, non-biological matter and energy."

Xu Heng, "What about the nutritional structure?"

Yue Pingting, "Food Chains and Food Webs."

Xu Heng, "So what?"

Yue Pingting frowned, very ambiguous.

Xu Heng, "In this way, let's look at one option and another. A. A complete ecosystem should also include non-biological matter and energy, so it's wrong! B..."

"So what's the choice for this question?"

Yue Pingting grumbled with her small face, her eyes widened, "So choose C!"

A look of grievance.

Xu Heng, "It's about studying, it's about studying, you girl, what are you thinking about?"