a, Ta có  10 30 = 10 3 10 = 1000 10

2 100 = 2 10 10 = 1024 10

Vì 1000<1024 nên  1000 10 <  1024 10

Vậy  10 30 <  2 100

b, Ta có:  333 444 = 333 4 111 = 3 . 111 4 111 =  81 . 111 4 111

444 333 = 444 3 111 = 4 . 111 3 111 =  64 . 111 3 111

Vì 81 > 64 và  111 4 > 111 3 nên  81 . 111 4 111 > 64 . 111 3 111

Vậy  333 444 > 444 333

c, Ta có:  21 5 = 3 . 7 15 = 3 15 . 7 15

27 5 . 49 8 = 3 3 5 . 7 2 8 = 3 15 . 7 16

Vì  7 15 < 7 16 nên  3 15 . 7 15 < 3 15 . 7 16

Vậy  21 5 <  27 5 . 49 8

d, Ta có:  3 2 n = 3 2 n = 9 n

2 3 n = 2 3 n = 8 n

Vì 8 < 9 nên  8 n < 9 n n ∈ N *

Vậy  3 2 n >  2 3 n

e, Ta có: 2017.2018 = (2018–1).(2018+1) = 2018.2018+2018.1–1.2018–1.1

=  2018 2 - 1

Vì  2018 2 - 1 < 2018 2 nên 2017.2018< 2018 2

f, Ta có:  100 - 99 2000 = 1 2000 = 1

100 + 99 0 = 199 0 = 1

Vậy  100 - 99 2000 =  100 + 99 0

g, Ta có:  2009 10 + 2009 9 = 2009 9 . 2009 + 1

=  2010 . 2009 9

2010 10 = 2010 . 2010 9

Vì  2009 9 < 2010 9 nên  2010 . 2009 9 <  2010 . 2010 9

Vậy  2009 10 + 2009 9 <  2010 10

Bài 1 

Mình làm mẫu một số câu thôi nhé

\(9,\sqrt{5}=\left(\sqrt{5}\right)^2=5\\ \sqrt{6}=\left(\sqrt{6}\right)^2=6\)

Vì \(5< 6\)

\(\Rightarrow\sqrt{5}< \sqrt{6}\)

\(10,2\sqrt{5}=\left(2\sqrt{5}\right)^2=20\\ \sqrt{7}=\left(\sqrt{7}\right)^2=7\)

Vì \(20>7\)

\(\Rightarrow2\sqrt{5}>\sqrt{7}\)

\(11,5\sqrt{2}=\left(5\sqrt{2}\right)^2=50\\ 2\sqrt{3}=\left(2\sqrt{3}\right)^2=12\)

Vì \(50>12\Rightarrow5\sqrt{2}>2\sqrt{3}\)

\(12,2\sqrt{6}=\left(2\sqrt{6}\right)^2=24\\ 5=5^2=25\)

Vì \(25>24\Rightarrow5>2\sqrt{6}\)

\(13,\sqrt{7}=\left(\sqrt{7}\right)^2=7\\ 2=2^2=4\)

Vì \(7>4\Rightarrow\sqrt{7}>2\)

\(14,3=3^2=9\\ \sqrt{5}=\left(\sqrt{5}\right)^2=5\)

Vì \(9>5\Rightarrow3>\sqrt{5}\)

\(15,3\sqrt{6}=\left(3\sqrt{6}\right)^2=54\)

Vì \(54>1\Rightarrow3\sqrt{6}>1\)

\(16,2\sqrt{2}=\left(2\sqrt{2}\right)^2=8\\ 3=3^2=9\)

Vì \(8< 9\Rightarrow2\sqrt{2}< 3\)

Phương pháp làm dạng bài này là bình phương hai vế rồi so sánh 

Bài 2

Gợi ý : Biểu thức dưới dấu căn \(\ge\) 0

Lưu ý : Nếu biểu thức dưới dấu căn ở dưới mẫu thì \(>0\)

\(21,ĐK:4x^2-12x+9>0\\ \Rightarrow\left(2x-3\right)^2>0\\ \Leftrightarrow x\ne\dfrac{3}{2}\)

\(22,ĐK:x^2-8x+15\ge0\\ \Rightarrow\left[{}\begin{matrix}x\le3\\x\ge5\end{matrix}\right.\)

\(23,ĐK:\left\{{}\begin{matrix}x-2\ge0\\x-5\ne0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x\ge2\\x\ne5\end{matrix}\right.\)

\(24,ĐK:\left\{{}\begin{matrix}\dfrac{2+x}{5-x}\ge0\\5-x\ne0\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}2+x\ge0\\5-x\ge0\\x\ne5\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x\ge-2\\x\le5\\x\ne5\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x\ge-2\\x< 5\end{matrix}\right.\left(t/m\right)\)

Hoặc

\(\left\{{}\begin{matrix}2+x\le0\\5-x\le0\\5-x\ne0\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x\le-2\\x\ge5\\x\ne5\end{matrix}\right.\left(loại\right)\)

Chỉ đăng tối đa 10 - 15 câu hỏi thôi, câu trước GV nhắc bạn rồi mà giờ bạn vẫn còn đăng nữa thì nên bị xóa câu hỏi. 

1.

a) Mary is as thin as her brother.

b) A lemon is not as sweet as an orange.

c) A donkey cannot run as quick as a horse.

d) This dress is twice as pretty as that one.

e)They don't drive a car as dangerous as us.

1. So sánh ngang bằng.

a. Mary/thin/her brother.

Mary is as thin as her brother.

b. A lemon/not sweet/ an orange. 

A lemon isn't as sweet as an orange.

c. A donkey/not run/quick/ a horse.

A donkey doesn't run as quickly as a horse.

d. This dress/twice/pretty/that one.

This dress is twice as pretty as that one.

e. They/ drive a car/ dangerous/ we.         

They drive a car as dangerously as we do.

2. So sánh hơn: (Nhấn mạnh các câu ss hơn)

a. this film /popular/ that one.       

This film is much more popular than that one.

b. A bird/can fly/slow/ a plane.

A bird can fly much more slowly than a plane.

c. Ba/ friendly/ Nam.

Ba is much more friendly than Nam.

d .Your house/far/from school /my house.

Your house is much farther from school than my house.

e. My father / drive/ careful/ I

My father drives much more carefully than I do.

3. So sánh nhất: (Nhấn mạnh theo 2 cách đã học)

a. This road/short /way/ in the city.

This road is by far the shortest way in the city.

b. Lan/ walk/ slow / in my class.

Lan walks by far the most slowly in my class.

c. Indian tea/bad/ of all.

Indian tea is by far the worst of all.

d. Anna/ work/ simple/girl/ in the world.

Anna works by far the simplest girl in the world.

e. Jack/ can tell/ the stories/ humourous/ in the world.

Jack can tell the stories by far the most humorously in the world.

II. Rewrite these sentences

1.      This street is narrower than that one

Þ    That street isn't as wide as this one.

Þ    That street is wider than this one.

2. Linda drives more carefully than Peter

Þ    Peter doesn't drive as carefully as Linda.

Þ    Peter drives more carelessly than Linda.

3.Your car is more convenient than mine

Þ    My car isn't as convenient as yours.

Þ    My car is less convenient than yours.

4. We behave more politely than her

Þ    She doesn't behave as politely as us.

Þ    She behaves more impolitely than us.

5.I  cook better than my mother

Þ    my mother doesn't cook as well as me.

Þ    my mother cooks worse than me.

6. Anna isn’t as confident as me

=> I am more confident than Anna.

7. This book isn’t as boring as that one

Þ    That book is more boring than this one.

8. I don’t work as effectively as he does

=> He works more effectively than I do.

9. My bedroom isn’t so comfortable as yours

Þ    Your bedroom is more comfortable than mine.

10. John didn’t speak English as well as Mary

=> Mary spoke English better than John.

11. Peter can dance the most gracefully in my city

=> No one in my city can dance as gracefully as Peter.

=> No one in my city can dance more gracefully than Peter.

12. Kangaroo is the most unique animal in the world

=> No animal in the world is as unique as kangaroo.

=> No animal in the world is more unique than kangaroo.

13. No river in the world is longer than Nile

=> Nile is the longest river in the world.

14. No student in my class learns Maths more intelligently than John

=> John learns Maths the most intelligently in my class.

15. If you read many books, you will have much knowledge

→ The more books you read, the more knowledge you will have.

16. He speaks too much and people feel bored.

→ The more he speaks, the more bored people feel.

2. 

a) This film is more popular than that one.

b) A bird can fly slower that a plane.

c) Ba is more friendly than Nam.

d) Your house is farther from school than my house.

e) My father drives more careful than I.

Ta có:

2009²⁰ = 2009¹⁰.2009¹⁰ < 2009¹⁰.10001¹⁰ = 20092009¹⁰

=> 2009²⁰ < 20092009¹⁰

2009^20 = 20092009^10

mik nghĩ là thế, không đúng thì thôi, đúng thì chọn mik nha

mik mới khôi phục đc điểm âm mà giờ bị âm tiếp, các bạn giúp mik nha, giúp mik thì mik sẽ giúp lại

cảm ơn trc

lỗi!

17 / 4 và 39/10 

ta sẽ thấy 17/4 ... 17/10 

dấu >

tiếp theo ta so sánh 

ta sẽ thấy 39 / 4 và 39/10

ta điền dấu > 

LƯU Ý : MUỐN TÌM PHÂN SỐ TRUNG GIAN TA LẤY TỬ SỐ CỦA PHÂN SỐ THỨ NHẤT GHÉP VỚI MẪU SỐ CỦA PHÂN SỐ THỨ HAI .

- Lượng mưa trung bình năm thấp (dưới 500mm/năm) nên rất khô hạn

- Biên độ nhiệt ngày và năm lớn

- Ít dân cư sinh sống, thực động vật nghèo nàn

=> Đới lạnh: được coi như hoang mạc, nhưng nhiệt độ quá thấp nên gọi là hoang mạc lạnh.