Với a,b,c,d là các số nguyên dương ta luôn có :

\(\frac{a}{a+b+c+d}< \frac{a}{a+b+c}< \frac{a+d}{a+b+c+d}\)

Tương tự : \(\frac{b}{a+b+c+d}< \frac{b}{b+c+d}< \frac{b+a}{a+b+c+d}\)

\(\frac{c}{a+b+c+d}< \frac{c}{c+d+a}< \frac{c+b}{a+b+c+d}\)

\(\frac{d}{a+b+c+d}< \frac{d}{d+a+b}< \frac{d+c}{a+b+c+d}\)

Cộng vế với vế ta được :

\(\frac{a+b+c+d}{a+b+c+d}< S< \frac{2.\left(a+b+c+d\right)}{a+b+c+d}\rightarrow1< S< 2\)

Do đó , S không là số tự nhiên.

\(\frac{d}{ưưda}ư\)

Thôi ko cần nữa đâu!!!!!

bạn đăng câu trả lời đi

B = \(\frac{-1}{9}\). \(\frac{-17}{29}\). \(\frac{58}{51}\)= \(\frac{2}{27}\)

D = \(\frac{-184}{9}\)

Nếu cần cách làm cụ thể thì ib tớ nhé, xl vì tớ không bt bấm cách làm cụ thể !!!:))

#Cụ_Maiz

\(B=\frac{-1}{9}.\frac{-17}{29}.\frac{58}{51}\)

\(=\frac{1.27.58}{9.29.51}\)

\(=\frac{1.27.29.2}{9.29.17.3}\)

\(=\frac{2}{27}\)

\(D=\left(1\frac{1}{27}.\frac{12}{23}.\frac{9}{14}\right):\left(\frac{-3}{23}\right)\)

\(=\frac{28}{27}.\frac{12}{23}.\frac{9}{14}.\left(\frac{-23}{3}\right)\)

\(=\frac{7.4.2.2.3.9.\left(-23\right)}{9.3.23.7.2.3}\)

\(=\frac{-8}{3}\)

Học tốt nhé

Xét dãy tích P₁ ta thấy 2 thừa số đều âm

=> P₁ dương <=> P₁ > 0

Xét dãy tích P₂ ta thấy có 3 thừa số âm

=> P₂ âm <=> P₂ < 0

XXets dãy P₃ thấy trong đó có một thừa số là \(\frac{0}{11}=0\)

=> P₃ = 0

Vậy P₂ < P₃ < P₁

P₁ có 2 thừa số âm => P₁ là số dương

P₂ có 3 thừa số âm => P₂ là số âm

P₃ có 1 thừa số \(\frac{0}{11}\)=> P₃=0

Từ đây suy ra P₂<P₃<P₁

sai bet thang ngu nhu cho

a) \(4\frac{5}{9}:\left(-\frac{5}{7}\right)+\frac{49}{9}:\left(-\frac{5}{7}\right)=\frac{41}{9}:\left(-\frac{5}{7}\right)+\frac{49}{9}:\left(-\frac{5}{7}\right)\)

\(=\frac{41}{9}\cdot\left(-\frac{7}{5}\right)+\frac{49}{9}\cdot\left(-\frac{7}{5}\right)=\left(\frac{41}{9}+\frac{49}{9}\right)\cdot\left(-\frac{7}{5}\right)=10\cdot\left(-\frac{7}{5}\right)=-14\)

b) \(\left(\frac{-3}{5}+\frac{4}{9}\right):\frac{7}{11}+\left(\frac{-2}{5}+\frac{5}{9}\right):\frac{7}{11}\)

\(=\left(\frac{-3}{5}+\frac{4}{9}+\frac{-2}{5}+\frac{5}{9}\right):\frac{7}{11}\)

\(=\left(\frac{-3}{5}+\frac{-2}{5}+\frac{4}{9}+\frac{5}{9}\right):\frac{7}{11}\)

\(=\left(-1+1\right):\frac{7}{11}=0\cdot\frac{11}{7}=0\)

c) \(\left(\frac{3}{4}\right)^4\cdot\left(\frac{8}{9}\right)^2=\left(\frac{3}{4}\right)^2\cdot\left(\frac{3}{4}\right)^2\cdot\left(\frac{8}{9}\right)^2=\left(\frac{3}{4}\cdot\frac{3}{4}\cdot\frac{8}{9}\right)^2\)

\(=\left(\frac{1}{2}\right)^2=\frac{1}{4}\)

d) \(\left(-\frac{3}{5}\right)^6\cdot\left(-\frac{5}{3}\right)^5=\left(-\frac{3}{5}\right)^5\cdot\left(-\frac{3}{5}\right)\cdot\left(-\frac{5}{3}\right)^5=\left[\left(-\frac{3}{5}\right)\cdot\left(-\frac{5}{3}\right)\right]^5\cdot\left(-\frac{3}{5}\right)\)

\(=1^5\cdot\left(-\frac{3}{5}\right)=1\cdot\left(-\frac{3}{5}\right)=-\frac{3}{5}\)

e) \(\frac{8^{14}}{4^4\cdot64^5}=\frac{\left(2^3\right)^{14}}{\left(2^2\right)^4\cdot\left(2^6\right)^5}=\frac{2^{42}}{2^8\cdot2^{30}}=\frac{2^{42}}{2^{38}}=2^4=16\)

f) \(\frac{9^{10}\cdot27^7}{81^7\cdot3^{15}}=\frac{\left(3^2\right)^{10}\cdot\left(3^3\right)^7}{\left(3^4\right)^7\cdot3^{15}}=\frac{3^{20}\cdot3^{21}}{3^{28}\cdot3^{15}}=\frac{3^{41}}{3^{43}}=3^{-2}=\frac{1}{3^2}=\frac{1}{9}\)

can goc nhon on roi tinh thoi ............vi .........................nen chon vay thoi

bạn quyên quyên chơi j kì vậy

I. Choose the underlined word or phrase (marked A, B, C or D) in each sentence that needs correcting.

1. The children are playing boarding games, and their mother is arranging flowers. => board

A                      B                      C                                 D                 

2. One of his father's favourite hobbies is playing horse-riding, and he just practises it  => bỏ playing 

A                                                 B              C

twice a month.

 D

3. He started learning how to play the guitar on his elder brother. => from 

A                                     B              C              D

4.Your favourite football match will begin at 3 p.m., so you should arrive there => start

                                                     A                          B                      C

soon to get a good seat.

D

5. She will attend the judo class next month because she intends to have a long => won't 

A                                                        B                           C

vacation in Ho Chi Minh City.

D

6. He loves to listen to classical music, but he spends a little time doing it. => listening

A                                        B           C                             D

7. She didn't enjoy the party very much because she didn't  music and

A                                                   B                                    C

to dance there. => dance

D

8.  She’s 18 and she’s France. She lives in a village near Toulouse. She studies => French

                                          A               B                                                             C                   

     engineering at university.

D

9.  She has a short black hair and very dark eyes. She is intelligent and funny, but => bỏ : a 

A                                        B                                     C                   

 sometimes she’s a bit sad too.

D

10.     She loves music and she s writing songs. She can plays the guitar very well and => play 

A                                        B           C                   

she has a beautiful voice.

D

* Xin lỗi ~~ Mình còn thiếu :

II. There is one mistake in each sentence. Underline and correct the mistake.

F. READING

I.  Read the text and choose the correct answer.

     If you enjoy cycling for pleasure, doing it in London can be a shock. There are not enough lanes especially for bikes, and making your way through the traffic can be very risky. But if you have great passion, cycling in London can be exciting, and it is an inexpensive way of keeping fit if you live there. Some cyclists don’t mind spending a lot of money on expensive bikes. However, if you just want a basic bike that is only for occasional use, there are many cheap choices. Several markets have cheap bikes on sale which may not be impressive to look at but should be satisfactory. You should buy a cycling helmet if you want to cycle in London. Wearing a cycling helmet is not compulsory in Britain, but it is a good idea to wear one for protection.

     1. What is the main idea of the passage?

          A. Cycling helmets                            B. Cheap bicycles

          C. Bicycle markets                            D. Cycling in London

     2. According to the passage, cycling in London is

          A. easy                 B. difficult            C. tiring                D. boring

     3. The word “it” in line 3 refers to

          A. cycling   B. passion  C. exc

- Nhyy-