Bài 1: Viết các đơn vị đo khối lượng sau dướ dạng số đo có đơn vị là km.

a, 2345dm= 0,2345km b, 3056m= 3,056km

b. 203cm= 0,00203km d. 12hm= 1,2km

Bài 2: Điền vào chỗ chấm sao cho thích hợp

a. 2345kg = 2,345 tấn

b. 540dag= 0,054 tạ

p. 346g = 0,0346 yến

Bài 3: Điền vào chỗ chấm sao cho thích hợp

a. 1023dm = 1,023hm

p. 302cm= 0,302dam

b. 246mm= 2,46dm

Bài 4: Viết các số thập phân thích hợp điền vào chỗ chấm:

23m56cm = 23,56m

b. 3dm4mm =3,04dm

b. 15km 25m = 15,025km

Bài 1:
a) Ta có:
\(a=\dfrac{v-v_0}{t-t_0}=\dfrac{10-50}{20}=-2\) (m/\(s^2\))
=> PTCĐ: \(x=x_0+v_0t+\dfrac{1}{2}at^2\)
  \(\Leftrightarrow\)   \(x=50t+\dfrac{1}{2}.\left(-2\right).t^2\)
  \(\Leftrightarrow\)   \(x=50t-t^2\)
b) Quảng đường vật đi được:
\(S=v_0+\dfrac{1}{2}at^2\)\(=50.20+\dfrac{1}{2}.\left(-2\right).20^2=600\) (m)

Refer 

I love sudying English so I want to visit Australia - an English speaking country.

Australia is a country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the world's sixth-largest country by total area. Although Australia has no official language, English has always been entrenched as the national language.

tham khảo 

Australia is the smallest of the six continents and the only one having ‘one country’ in it. It remained cut off from the rest of the world after its geologic separation from Gondwanaland and its great distance from Europe, Americas and Asia. As a result very strange flora and fauna developed on this continent. It mostly consists of a flat, featureless land with no great rivers and no permanent snow covered mountains. The central lowlands are known for their underground water in their artesian basins. The Great Barrier Reef made up of coral rocks is a great tourist attraction.
Seasons in Australia are reverse of India because of the former’s location in Southern Hemisphere. It is mostly hot and dry as only 4% of the land is under cultivation. Wheat is grown extensively on the temperate grasslands in the Murray-Darling basin. Eucalyptus is the most common tree; nearly 700 varieties are found. The people have managed their limited land and water resources well.
Although the average density of the population is very low, most people live in the large cities and ports of the rainy eastern and south-eastern regions. Although the population is not much, Australia produces enough agricultural and industrial goods to meet its needs and still has plenty for export to other countries of the world.

TK: Australia is the smallest of the six continents and the only one having ‘one country’ in it. It remained cut off from the rest of the world after its geologic separation from Gondwanaland and its great distance from Europe, Americas and Asia. As a result very strange flora and fauna developed on this continent. It mostly consists of a flat, featureless land with no great rivers and no permanent snow covered mountains. The central lowlands are known for their underground water in their artesian basins. The Great Barrier Reef made up of coral rocks is a great tourist attraction.

Seasons in Australia are reverse of India because of the former’s location in Southern Hemisphere. It is mostly hot and dry as only 4% of the land is under cultivation. Wheat is grown extensively on the temperate grasslands in the Murray-Darling basin. Eucalyptus is the most common tree; nearly 700 varieties are found. The people have managed their limited land and water resources well.
Although the average density of the population is very low, most people live in the large cities and ports of the rainy eastern and south-eastern regions. Although the population is not much, Australia produces enough agricultural and industrial goods to meet its needs and still has plenty for export to other countries of the world.

1 are

2 am

3 is

4 are

5 are

6 are

7 is

8 is

9 is

10 are

IV

1 is writing

2 are losing

3 is having

4 is staying

5 am not lying

6 is always using

7 are having

8 Are you playing

9 are not touching

10 Is - listening

11 Is- winning

12 am not staying

13 is not working

14 is not reading

15 isn't raining

16 am not listening

17 Are they making

18 Are you doing

19 Is - sitting

20 is - doing

21 are-putting

22 are-wearing

23 is-studying

2, am

3, is

4,are

5,are

6,are

7,is

8,is

9,is

10,are

IV

1,2,7 OK

3,is having

4,has stayed

5,am not lying

6,always uses

8,Are-playing

9,not to touch

10,Is-listening

11,Are-winning

12,am not staying

13,isn't working

14,isn't reading

15,isn't raining

16,am not listening

17,Are-making

18,Are-doing

19,Is-sitting

20,is-doing

21,do-putting

22,do-wear

23,is-studying

gõ câu hỏi ra đi bạn 

1. a) 6² : 4 . 3 + 2 . 5²

= 36 : 4 . 3 + 2 . 25

= 9 . 3 + 50

= 27 + 50

= 77

b) 5 . 4² - 32 : 4²

= 5 . 16 - 32 : 16

= 80 - 2

= 78

c) 80 - (4 . 5² - 3 .2³)

= 80 - (4 . 25 - 3 . 8)

= 80 - (100 - 24)

= 80 - 76

= 4

d) 2448 : [119 - (23 - 6)]

= 2448 : (119 - 17)

= 2448 : 102

= 24

e) 23 . 85 + 15 . 23 + 170

= 23 . (85 + 15) + 170

= 23 . 100 + 170

= 2300 + 170

= 2470

f) 3³ . 2  - 5 . 2023⁰ + 36 : 3²

= 27 . 2 - 5 . 1 + 36 : 9

= 54 - 5 + 4

= 53

2. a) 123 - 5.(x + 4) = 38

5.(x + 4) = 123 - 38

5.(x + 4) = 85

x + 4 = 85 : 5

x + 4 = 17

x = 17 - 4

x = 13

b) (3.x - 2⁴) . 7³ = 2 . 7⁴

3x - 16 = 2 . 7⁴ : 7³

3x - 16 = 2 . 7

3x = 14 + 16

3x = 30

x = 30 : 3

x = 10

c) (2600 + 6400) - 3.x = 1200

9000 - 3x = 1200

3x = 9000 - 1200

3x = 7800

x = 7800 : 3

x = 2600

d) [(6.x - 72) : 2 - 84] . 28 = 5628

(6x - 72) : 2 - 84 = 5628 : 28

(6x - 72) : 2 - 84 = 201

(6x - 72) : 2 = 201 + 84

(6x - 72) : 2 = 285

6x - 72 = 285 . 2

6x - 72 = 570

6x = 570 + 72

6x = 642

x = 642 : 6

x = 107

e) 70 - 5(x - 3) = 45

5(x - 3) = 70 - 45

5(x - 3) = 25

x - 3 = 25 : 5

x - 3 = 5

x = 5 + 3

x = 8

f) 10 + 2.x = 4⁷ : 4⁵

10 + 2x = 4²

10 + 2x = 16

2x = 16 - 10

2x = 6

x = 6 : 2

x = 3

g) 2.x - 138 = 2³.2²

2x - 138 = 2⁵

2x - 138 = 32

2x = 32 + 138

2x = 170

x = 170 : 2

x = 85

h) 231 - (x - 6) = 1339 : 13

231 - (x - 6) = 103

x - 6 = 231 - 103

x - 6 = 128

x = 128 + 6

x = 134

1.Tính:

a) \(6^2:4.3+2.5^2\)

\(=36:4.3+2.25\)

\(=9.3+50\)

\(=27+50\)

\(=77\)

b) \(5.4^2-32:4^2\)

\(=5.16-32:16\)

\(=80-2\)

\(=78\)

c) \(80-\left(4.5^2-3.2^3\right)\)

\(=80-\left(4.25-3.8\right)\)

\(=80-\left(100-24\right)\)

\(=80-76\)

\(=4\)

d) \(2448:\left[119-\left(23-6\right)\right]\)

\(=2448:\left[119-17\right]\)

\(=2448:102\)

\(=24\)

e) \(23.85+15.23+170\)

\(=23\left(85+15\right)+170\)

\(=23.100+170\)

\(=2300+170\)

\(=2470\)

f) \(3^3.2-5.2023^0+36:3^2\)

\(=27.2-5.1+36:9\)

\(=54-5+4\)

\(=53\)

2. Tìm x biết:

a) \(123-5.\left(x+4\right)=38\)

\(=>5.\left(x+4\right)=123-38\)

\(=>5.\left(x+4\right)=85\)

\(=>x+4=85:5\)

\(=>x+4=17\)

\(=>x=17-4\)

\(=>x=13\)

b) \(\left(3.x-2^4\right).7^3=2.7^4\)

\(=>3.x-2^4=2.7^4:7^3\)

\(=>3.x-2^4=2.7\)

\(=>3.x-16=14\)

\(=>3.x=14+16\)

\(=>3.x=30\)

\(=>x=30:3\)

\(=>x=10\)

c) \(\left(2600+6400\right)-3.x=1200\)

\(=>9000-3.x=1200\)

\(=>3.x=9000-1200\)

\(=>3.x=7800\)

\(=>x=7800:3\)

\(=>x=2600\)

d) \(\left[\left(6.x-72\right):2-84\right].28=5628\)

\(=>\left(6.x-72\right):2-84=5628:28\)

\(=>\left(6.x-72\right):2-84=201\)

\(=>\left(6.x-72\right):2=201+84\)

\(=>\left(6.x-72\right):2=285\)

\(=>6.x-72=285\times2\)

\(=>6.x-72=570\)

\(=>6.x=570+72\)

\(=>6.x=642\)

\(=>x=642:6\)

\(=>x=107\)

e) \(70-5.\left(x-3\right)=45\)

\(=>5.\left(x-3\right)=70-45\)

\(=>5.\left(x-3\right)=25\)

\(=>x-3=25:5\)

\(=>x-3=5\)

\(=>x=5+3\)

\(=>x=8\)

f) \(10+2.x=4^7:4^5\)

\(=>10+2.x=4^2\)

\(=>10+2.x=16\)

\(=>2.x=16-10\)

\(=>2.x=6\)

\(=>x=6:2\)

\(=>x=3\)

g) \(2.x-138=2^3.3^2\)

\(=>2.x-138=8.9\)

\(=>2.x-138=72\)

\(=>2.x=72+138\)

\(=>2.x=210\)

\(=>x=210:2\)

\(=>x=105\)

h) \(231-\left(x-6\right)=1339:13\)

\(=>231-\left(x-6\right)=103\)

\(=>x-6=231-103\)

\(=>x-6=128\)

\(=>x=128+6\)

\(=>x=134\)

Chúc bạn học tốt

Câu 3: 

a: Ta có: \(2x\left(3x-1\right)-\left(x-3\right)\left(6x+2\right)\)

\(=6x^2-2x-6x^2-2x+18x+6\)

=14x+6

b: Ta có: \(2x\left(x+7\right)-3x\left(x+1\right)\)

\(=2x^2+14x-3x^2-3x\)

\(=-x^2+11x\)

Câu 2: 

a: Ta có: \(\left(-8x^5+12x^3-16x^2\right):4x^2\)

\(=-8x^5:4x^2+12x^3:4x^2-16x^2:4x^2\)

\(=-2x^3+3x-4\)

b: Ta có: \(\left(12x^3y^3-18x^2y+9xy^2\right):6xy\)

\(=12x^3y^3:6xy-18x^2y:6xy+9xy^2:6xy\)

\(=2x^2y^2-3x+\dfrac{3}{2}y\)

c: Ta có: \(\dfrac{x^3-11x^2+27x-9}{x-3}\)

\(=\dfrac{x^3-3x^2-8x^2+24x+3x-9}{x-3}\)

\(=x^2-8x+3\)

d: Ta có: \(\dfrac{6x^4-13x^3+7x^2-x-5}{3x+1}\)

\(=\dfrac{6x^4+2x^3-15x^3-5x^2+12x^2+4x-5x-\dfrac{5}{3}-\dfrac{10}{3}}{3x+1}\)

\(=2x^3-5x^2+4x-\dfrac{5}{3}-\dfrac{\dfrac{10}{3}}{3x+1}\)