Nội qui tham gia "Giúp tôi giải toán"

1. Không đưa câu hỏi linh tinh lên diễn đàn, chỉ đưa các bài mà mình không giải được hoặc các câu hỏi hay lên diễn đàn;

2. Không trả lời linh tinh, không phù hợp với nội dung câu hỏi trên diễn đàn.

3. Không k "Đúng" vào các câu trả lời linh tinh nhằm gian lận điểm hỏi đáp.

Các bạn vi phạm 3 điều trên sẽ bị giáo viên của Online Math trừ hết điểm hỏi đáp, có thể bị khóa tài khoản hoặc bị cấm vĩnh viễn không đăng nhập vào trang web.

                                      Nếu bạn muốn học hiệu quả thì bạn cần có những kĩ năng như

tư duy , phân tích hay tập trung.Những kĩ năng có được hình thành qua thói quen của bạn hay nói chính xác hơn thì đó chính là

phản xạ có điều kiện mà bạn sẽ được học ở sách sinh học 8 :3333333

 Chúc bạn thành công !

a, \(\left(x-1\right)\left(y+1\right)=5\)

\(\Leftrightarrow x-1;y+1\inƯ\left(5\right)=\left\{\pm1;\pm5\right\}\)

d, \(\left(3-x\right)\left(xy+5\right)=-1\)

\(\Leftrightarrow3-x;xy+5\inƯ\left(-1\right)=\left\{\pm1\right\}\)

f, \(\left(x-7\right)\left(y+2\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x-7=0\\y+2=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=7\\y=-2\end{cases}}}\)

Bn làm nốt nhé ! 

a, \(\left(x-1\right)\left(y+1\right)=5\)

\(< =>\left(x-1\right)\left(y+1\right)=1.5=5.1=-1.\left(-5\right)=-5.\left(-1\right)\)

Vậy ta có các cặp số x,y thỏa mãn đk sau : ...

b, \(\left(x+2\right)\left(y-3\right)=-3\)

\(< =>\left(x+2\right)\left(y-3\right)=-1.3=-3.1\)

Vậy ta có các cặp số x,y thỏa mãn đk sau : ...

c, \(\left(x+2\right)\left(y-1\right)=3\)

\(< =>\left(x+2\right)\left(y-1\right)=1.3=3.1=-1.\left(-3\right)=-3.\left(-1\right)\)

Vậy ta có các cặp số x,y thỏa mãn đk sau : ...

d,\(\left(3-x\right)\left(xy+5\right)=-1\)

\(< =>\left(3-x\right)\left(xy+5\right)=1.\left(-1\right)=-1.1\)

Vậy ta có các cặp số x,y thỏa mãn đk sau : ...

2 câu sau dễ tự làm

C = 1.2 + 2.3 + 3.4 + ... + 198.199

=> 3C = 1.2.3 + 2.3.3 + 3.4.3 + ... + 198.199.3

=> 3C = 1.2.3 + 2.3.(4 - 1) + 3.4.(5 - 2) + ... + 198.199.(200 - 197)

=> 3C = 1.2.3 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 + ... + 198.199.200 - 197.198.199

=> 3C = 198.199.200

=> 3C = 7 880 400

=> C = 2 626 800

a, \(\left|x-3\right|-16=-4\Leftrightarrow\left|x-3\right|=12\)

\(\Leftrightarrow\orbr{\begin{cases}x-3=12\\x-3=-12\end{cases}\Leftrightarrow\orbr{\begin{cases}x=15\\x=-9\end{cases}}}\)

b, \(26-\left|x+9\right|=-13\Leftrightarrow\left|x+9\right|=39\)

\(\Leftrightarrow\orbr{\begin{cases}x+9=39\\x+9=-39\end{cases}\Leftrightarrow\orbr{\begin{cases}x=30\\x=-48\end{cases}}}\)

f, \(9x+25=-\left(2x-58\right)\Leftrightarrow9x+25=-2x+58\)

\(\Leftrightarrow11x-33=0\Leftrightarrow x=3\)

Làm nốt nhé ! 

a. \(\left|x-3\right|-16=-4\)

\(\Rightarrow\left|x-3\right|=12\)

\(\Rightarrow\orbr{\begin{cases}x-3=12\\x-3=-12\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=15\\x=-9\end{cases}}\)

b. \(26-\left|x+9\right|=-13\)

\(\Rightarrow\left|x+9\right|=39\)

\(\Rightarrow\orbr{\begin{cases}x+9=39\\x+9=-39\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=30\\x=-48\end{cases}}\)

c. \(5-\left(10-x\right)=7\)

\(\Rightarrow10-x=-2\)

\(\Rightarrow x=12\)

d. \(11+\left(15-x\right)=1\)

\(\Rightarrow15-x=-10\)

\(\Rightarrow x=25\)

e. \(8x-75=5x+21\)

\(\Rightarrow8x-5x=75+21\)

\(\Rightarrow3x=96\)

\(\Rightarrow x=32\)

f. \(9x+25=-\left(2x-58\right)\)

\(\Rightarrow9x+25=-2x+58\)

\(\Rightarrow9x+2x=58-25\)

\(\Rightarrow11x=33\)

\(\Rightarrow x=3\)

g. \(\left|x+3\right|=4\)

\(\Rightarrow\orbr{\begin{cases}x+3=4\\x+3=-4\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=1\\x=-7\end{cases}}\)

h. \(15-\left|2x-1\right|=\left|-8\right|\)

\(\Rightarrow15-\left|2x-1\right|=8\)

\(\Rightarrow\left|2x-1\right|=7\)

\(\Rightarrow\orbr{\begin{cases}2x-1=7\\2x-1=-7\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=4\\x=-4\end{cases}}\)

1) The police.....have arrested...............two people early this morning. (arrest)

2) She …has taught………….in this school since she …graduated……………from university. (teach/ graduate)

3) Dan.has.already .bought...............two tablets this year. (already/ buy)

4) How many games...have your team won..............so far this season? (your team/ win)

5)....Did you visit............the CN Tower when you...stayed.............in Toronto? (you/ visit - stay)

6)........Have you done............your homework yet? – Yes, I...finished..............it an hour ago. (you/ do - finish)

7) There...was.........an accident in High Street, so we have to use King Street to get to your school. (to be)

8) I....haven't seen...........Peter since I...arrived............last Tuesday. (not/ see - arrive)

9) Frank.....got.............his bike in May. So he...has had................it for 4 months. (get - have)

10) I'm sorry, I..did'n write................earlier, but I....have worked..............a lot lately. (not/ write - work)

11) Peter played football yesterday (play)

12) They cleaned the car. It looks new again. (clean)

13) Last year we...were............... to Italy. (be)

14) John and Peggy.....read................. the book. Now they can watch the film. (read)

15) I....met............. my friend two days ago. (meet)

16) We have never……visited……….... another country before. (visit)

17) She.....bought.................... a new car in 2011. (buy)

18) I'm sorry, but I...have forgotten........................ my homework. (forget)

19).....Have.......you.....won............. the game of chess? (win)

20) The girls......have eaten.................. their lunch yet. (eat)

1) The police arrested two people early this morning.
2) She went to Japan but now she has come back.
3) Dan has already bought two tablets this year.
4) How many games has your team won so far this season?
5) Did you visit the CN Tower when you stayed in Toronto?
6) Have your done your homework yet? – Yes, I finished it an hour ago.
7) There has been an accident in High Street, so we have to use King Street to get to your
school.
8) I have not seen Peter since I arrived last Tuesday.
9) Frank got his bike last May. So he has had it for 4 months.
10) I'm sorry, I have not written earlier, but I have worked a lot lately

41.How many rooms are there in Hoa's house?                                    46.she spends thirty minutes doing this test.                                 -->how many rooms..does..hoa's house have..................                     -->It takes.her.thirty minutes.to do this test.......................

42. this book is cheaper than my book.                                                 47.How much do these trousers cost?

-->my book is..more expensive than this book........                            -->what.is the price of..these trosusers ?.......................

43.who own this house                                                                          48. why don't we go swmming this afternoon?  

-->who does..this house belong to..?................                                        -->what about..going swimming this afternoon .?............... 

44. they to walk in the rain                                                               49. the weather was bad , so we decideto satay at home and 

-->they enjoy..walking in the rain very much........................                                                                      watch TV

45. Nam began learning English five year ago.                                          -->Because...the weather is bad , we decide to

                                                                                                                                .stay at home and watch TV..................

-->Nam has.learnt English for five years...................................                                                         

50. No one in my class is aintelligent as Huy. 

       -->Huy is..the most intelligent student in my class.........................

X. Rewrite the following sentences without changing the meaning, using the words given. 

41.How many rooms are there in Hoa's house?                                    46.she spends thirty minutes doing this test.                                 -->how many rooms does Hoa's house have?                                                          -->It take her thirty minutes  to do this test.

42. this book is cheaper than my book.                                                 47.How much do these trousers cost?

-->my book is is expensive                                                                                    -->what is the price of these trousers?

43.who own this house                                                                          48. why don't we go swmming this afternoon?  

-->who does  this house belong to?                                                                 -->what about going swimming this afternoon ?

44. they to walk in the sain                                                               49. the weather was bad , so we decideto satay at home and 

-->they enjoy walking in the sain                                                                     watch TV

45. Nam began learning English five year ago.                                          -->Because the weather is bad , we decide to stay at home

                                                                                                                         and watch TV

-->Nam has learnt  English  for five years                                                 50. No one in my class is an intelligent as Huy. 

                                                                                                                    -->Huy is the most intelligent in my class

Tính số chia hết cho 5 ,5^2;...5^n

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