y=-2x^2-3x+4

Hi cj iu ! Mà s cj onl muộn thế ,pé sắp ngủ òi !

Goij số hạt notron, proton, electron của nguyên tử Y lần lượt là N, P, E trong đó P = E

=> N + P + E =58

=> N + 2 E =58 (1)

Mặt khác: (N + P ) - ( E + P) =1

=> N - E = 1  (2)

Từ (1); (2) => N = 20 , E = P =19 

=> Y là nguyên tử K 

\(M\left(Z_1,N_2\right)vaX\left(Z_2,N_2\right)\)

\(2Z_1+N_1+2Z_2+N_2=108\)

\(2\left(Z_1+Z_2\right)-\left(N_1+N_2\right)=36\)

\(Z_1+N_1-Z_2-N_2=8\)
\(2Z_1+N_1-2-\left(2Z_2+N_2+2\right)=8\)

Từ hệ trên 

\(M\left(Z_1,N_1\right)\)nhé mình nhầm

\(\left(x^2+25+150\right)\left(x^2+30x+216\right)=2x^2\)

\(\Rightarrow\left[\left(x+12,5\right)^2-6,25\right]\left[\left(x+15\right)^2-9\right]=2x^2\)

\(\Rightarrow\left(x+15\right)\left(x+10\right)\left(x+18\right)\left(x+12\right)=2x^2\)

Đến đây tách như lớp 8 ,dài quá nên mk lười :) bạn tự giải nha

thanks làm tiếp để thế hệ sau tham khảo :

\(\Rightarrow\left(x+15\right)\left(x+12\right)\left(x+10\right)\left(x+18\right)=2x^2\)

\(\Rightarrow\left(x^2+27x+180\right)\left(x^2+28x+180\right)=2x^2\)

Chia cả hai vế cho x² 

\(\Rightarrow\left(x+27+\frac{180}{x}\right)\left(x+28+\frac{180}{x}\right)=2\)

Đặt \(a=x+\frac{180}{x}\)

\(\Rightarrow\left(a+27\right)\left(a+28\right)=2\)

\(\Rightarrow a^2+56a+756=2\)

\(\Rightarrow a^2+56a+754=0\)

tìm nghiệm rồi thế vào :

viết dc cái j

1. Are you a students , or do you have a job, or both?

I am a student at university, but because it is very expensive to go to university, I am forced to have a job to pay my fees and other expenses such as books and transport. In fact I am very lucky to have the chance of studying while I work because I get the best of both worlds, but it does mean a lot of pressure, and I have to burn the candle at both ends.
Idioms chất lượng:
• to have/ get the best of both worlds : nghĩa là bạn là người có thể trung hòa, có thể tận hưởng và kết hợp được hai thứ đối lập ở cùng một thời điểm. Đây là một cách nói rất hay mà người bản xứ hay dùng.
• to burn the candle at both ends : gặp nhiều áp lực vì sống một cuộc sống bận rộn.

2. What do you study?

I study law because it’s a really well thought of degree and I’m hoping to pursue it as a career in the future.
Từ ăn điểm:
Well though of: được đánh giá tốt

3. Is it a popular subject in your country?

Very popular, in fact it’s one of the most sought after courses. I think there are about 350 people reading law at Queen’s. I think lots of student’s parents want them to study law so they can get a good job after they graduate.

4. Do you that subject?

It’s such a huge subject that there will always be parts you and parts you don’t . I find Human Rights fascinating because it can really make a difference to peoples’ lives. On the other hand, modules Land Law and Equity are really boring.

5. Do you plan to use the subject you are studying in the future?

Yes, I’ve already started to apply for jobs as a lawyer. We normally have to secure a job a year before we graduate and then work very hard to get a high overall mark. After that, I will probably do a Masters in law to become a specialist in one parular area.
Từ ăn điểm:
secure a job: giữ được việc

6. What is the most difficult part of your subject?

You have to remember lots of legislation and cases and not only remember their names, but also how the affect each part of the law and how they interact with each other. Physically it can also be exhausting because we have to read very dense texts for a few hours every day.

7. What do you most about your studies?

I love spending time in class because I learn something new every day and I feel myself grow. It is quite challenging but very stimulating and I feel proud when I manage to solve some complicated exercise for homework.

8. Has your attitude to school/work/college changed since you started there?

I used to be very shy and introvert because my problem was that I had very little self confidence. Since I have been working and going to university, I have met loads of new people and this has helped me to look at life differently. I am more confident and more comfortable with people from different cultures, which is something very different from how I used to be.
Từ ăn điểm:
• Self confidence: tự tin
• To meet loads of sb: làm quen với nhiều người ( kết bạn với nhiều người).

9. What would to study in the future?

As I said before, my favourite type of law is Human Rights, so I would to do a masters in International Human Rights Law. it’s right at the cutting edge of my field and there are also lots of very high profile cases in the media, so it’s really exciting and something I would to become an expert in.
Từ ăn điểm:
Cutting edge: lĩnh vực mũi nhọn

10. If you had the chance, would you change subject?

I planned to study medicine, but then when I went on work experience I fainted at the first sight of blood, so definitely not that. I’m a real history buff and read books about World War 2 all the time, so I suppose it would have to be Modern History.

11. Why did you choose your university?

Mostly because it is close to my hometown and most of my friends were going there. I kind of regret it now. It’s a great university, but because it’s so close to home it doesn’t give you much of a chance to experience new things and meet new people. If I were to choose again, I’d study abroad.
12. What do you hope to do in the future when you have finished?
I’m not sure at the moment, but I may go into teaching. This is why I’m doing the IELTS, as I intend to carry on and do a Masters in a specific area of Law. I’ll probably decide for sure what to do when I have completed that.

!Tham khảo

Châu's ngốc

Có cách giải nhưng t ko chắc đâu nhá;) đã bảo đưa dạng a, b, c rồi mà cứ đưa dạng này-_-

\(VT< \sqrt{2\sqrt{3\sqrt{4\sqrt{5\sqrt{6....}}}}}=x>0\) (vô hạn dấu căn). Ta sẽ chứng minh x < 3

Ta thấy \(x^2=\sqrt{2}.x\Rightarrow x\left(x-\sqrt{2}\right)=0\Rightarrow x=\sqrt{2}< 3\Rightarrow\text{đpcm }\)

\(x^2=2\sqrt{3\sqrt{4\sqrt{5....\sqrt{2000}}}}ma?\)