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21 tháng 7 2023

\(S=1+2-3-4+5+6-7-8+9+10-...+2018-2019-2020+2021\)

\(S=0+1-1+1-1+...-1-+1=0\)

21 tháng 7 2023

Số phân số số trứng còn lại :

\(1-\dfrac{1}{4}-\dfrac{1}{3}-\dfrac{2}{5}=\dfrac{1}{60}\)

Số trứng tất cả đem bán :

\(10:\dfrac{1}{60}=10.60=600\) (trứng)

Số trứng lần 1 :

\(600x\dfrac{1}{4}=150\) (trứng)

Số trứng lần 2 :

\(600x\dfrac{1}{3}=200\) (trứng)

Số trứng lần 3 :

\(600x\dfrac{2}{5}=240\) (trứng)

21 tháng 7 2023

\(...=\dfrac{19}{4}km=\dfrac{19000}{4}m\)

21 tháng 7 2023

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6
AH
Akai Haruma
Giáo viên
21 tháng 7 2023

Bài 1:

Tổng của hai số: $1000$

Số lớn là: $1000:(3+5)\times 5=625$ 

Số bé là: $1000:(3+5)\times 3=375$

AH
Akai Haruma
Giáo viên
21 tháng 7 2023

Bài 2:

Tổng hai số: $60\times 2=120$ 

Số bé là: $120:(4+1)\times 1=24$ 

Số lớn là: $24\times 4=96$

21 tháng 7 2023

\(=3^3.3^n+3.3^n+2^3.2^n+2^2.2^n=\)

\(=3^n\left(3^3+3\right)+2^n\left(2^3+2^2\right)=30.3^n+12.2^n=\)

\(=6\left(5.3^n+2.2^n\right)⋮6\)

21 tháng 7 2023

\(3^{n+3}+3^{n+1}+2^{n+3}+2^{n+2}\)

\(=3^{n+1}\left(9+3\right)+2^{n+2}\left(8+4\right)\)

\(=12.3^{n+1}+12.2^{n+2}=12.\left(3^{n+1}+2^{n+2}\right)\)

mà 12⋮6

\(\Rightarrow12.\left(3^{n+1}+2^{n+2}\right)⋮6\Rightarrow dpcm\)

21 tháng 7 2023

...=-15-9=-24

...=4+7=11

...=-12-13=-25

...=13+10=23

...=-4-7=-11

...=-9+13=4

...=12+0=12

...=0-7=-7

...=0+3=3

...=15-17=-2

...=-6

...=-23

...=15-15=0

GH
21 tháng 7 2023

-15-(+9) = -24

4-(-7) = 11

-12+(-13) = -25

-(-13)-(-10) = 23

-4-(+7) = -11

(-9)-(-13) = 4

-(-12)+0 = 12

0-(+7) = -7

0-(-3) = 3

15-17 = -2

-18+12 = -6

-5-18 = -23

-(-15)+(-15) = 0

AH
Akai Haruma
Giáo viên
21 tháng 7 2023

Lời giải:

Phân số bé là:

$(\frac{33}{30}-\frac{1}{6}):2=\frac{7}{15}$

Phân số lớn là:
$(\frac{33}{30}+\frac{1}{6}):2=\frac{19}{30}$

21 tháng 7 2023

Số hạng thứ 22 là :

\(\left(22-1\right).3+7=73\)

Tổng : \(\left[\left(73-7\right):3+1\right]\left(73+7\right):2=23.80:2=920\)

21 tháng 7 2023

\(\left(2x-3\right)^2-\left(x+5\right)\left(4x-1\right)=-9\)

\(\Leftrightarrow4x^2-12x+9-4x^2+x-20x+5=-9\)

\(\Leftrightarrow-31x+14=-9\)

\(\Leftrightarrow-31x=-23\)

\(\Leftrightarrow x=\dfrac{-23}{-31}\)

\(\Leftrightarrow x=\dfrac{23}{31}\)

21 tháng 7 2023

\(\Leftrightarrow4x^2-12x+9-4x^2+x-20x-5=-9\)

\(\Leftrightarrow31x=13\Leftrightarrow x=\dfrac{13}{31}\)

1. What time do you go to school, Mai? A. Yes, at 6.45 a.m                 B. 6.45 a.m                C. At 2.45 a.m                 D. At 6.45 a.m 2. How many …………….do you have today ? A. sujects                         B. subjects                         C. pupils                           D. childrens 3. . My father ……………….a book last night . A. reads                          B. readed                              C. read                           D. rode 4. Nam is good ………….Music ,...
Đọc tiếp

1. What time do you go to school, Mai?

A. Yes, at 6.45 a.m                 B. 6.45 a.m                C. At 2.45 a.m                 D. At 6.45 a.m

2. How many …………….do you have today ?

A. sujects                         B. subjects                         C. pupils                           D. childrens

3. . My father ……………….a book last night .

A. reads                          B. readed                              C. read                           D. rode

4. Nam is good ………….Music , but he is bad……………….English .

A. at/ in                             B. in/ at                        C. at / to                           D. at / at

5. Where were you last Sunday ?

A. by taxi                         B. it’s Nam Dinh province          C. at school        D. two years ago

6. Will Nam be at school tomorrow ?

A. Yes, she is.                 B. Yes, he will.             C. She is .                          D. Yes, he is going.

7. We ………….. and ……………at the party yesterday .

A. sing/ dance                  B. sang/ danced              C. sings/ dances            D. sang/ dance

8. What is ………favourite colour ? I like red.

A. his                               B. her                               C. you                          D. your

 

9. …………………………………………? It’s Mrs Lien .

A. What subjects do you have today?                   B. How many pencils are there ?

C. Who is your English teacher ?                         D. Is she at school now ?

10. At school, we learn ………a lot of things.

A. in                                 B. at                        C. to                             D. about

11. He likes playing sports …………football and tennis.

 A. such as                       B. such like             C. sample                    D. example

12. What is Tam like ? ……………………………. .

A. She is cruel                 B. She is gentle and kind              C. She is brave      D. She is generous

13. The monkeys swing …………………….. from tree to tree .

A. loudly                        B. beautifully            C. quickly                  D. quietly

14. I went to my hometown ………………..motorbike .

A. by                               B. for                         C. at                            D. to

15. . His father always ………….coffee for breakfast.

A. drink                         B. drinks                    C. is drinking              D. are drinking

16. What foreign …………….do you have at school?

A. subject                     B. song                       C. language                 D. book

17. They would like some milk……….. dinner.

A. in                              B. at                          C. for                           D. of

18. How do you …………….. listening? – I watch English cartoons on TV.

A. practise                    B. learn                     C. want                    D. have

19. Where …………you usually…………..in the evening ?

 A. do / go                 B. are / go                    C. are  / going             D. do / going

20. When I see a new word, I try to guess its …………………

A. name                    B. vocabulary               C. meaning                 D. language

21. In ………………………….we learn how to use a computer.

A. science                 B. Music                     C. IT                            D. PE

22. How…………..do you brush your teeth ?

A. many                    B. often                         C. old                       D. time

23. He practices ……………English by ………………cartoons on TV .

A. Listening/ watching         B. listen / watch       C. watching/ listening      D.listens/ watches

24. The boy ……………….his teacher some beautiful flowers.

 A. like to give                     B. like giving            C. likes gives             D. would like to give

25. They write emails to _____ other every day.

A. every                                B. each                 C. one                      D. they

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21 tháng 7 2023

1) B      2) B     3) C      4)D      5) B     6 )B       7)B      8) D     9 ) C          10) A    11) B     12) B     13 ) C     14) A     15) A    16 ) C    17 ) C            18) B    19) B     20)D      21) C      22)B      23)A      24) B   25) B                  đây nhé bạn !!!