giúp mình bài này vs : so sánh 200910+20099và 201010
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CM
21 tháng 1 2017
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
H
19 tháng 6 2023
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
H
19 tháng 6 2023
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
\(\left\{{}\begin{matrix}2+x\le0\\5-x\le0\\5-x\ne0\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}x\le-2\\x\ge5\\x\ne5\end{matrix}\right.\left(loại\right)\)
7 tháng 8 2021
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.
7 tháng 8 2021
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.
NL
2
1 tháng 9 2016
Ta có:
200920 = 200910.200910 < 200910.1000110 = 2009200910
=> 200920 < 2009200910
và 
và 
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PA
28 tháng 6 2017
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 .
TN
1
TN
15 tháng 12 2020
- 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.
\(2009^{10}+2009^9=2009.2009^9+2009^9=2009^9.\left(2009+1\right)=2009^9.2010\)
\(2010^{10}=2010^9.2010\)
Vì \(2009^9