\(\left(a-2009\right)^2+\left(b+2010\right)^2=0\)

\(\Rightarrow\hept{\begin{cases}a-2009=0\\b+2010=0\end{cases}\Rightarrow\hept{\begin{cases}a=2009\\b=-2010\end{cases}}}\)

Vậy : ...................

Số bé là :

​( 55 - 13 ) : 2 = 21

​Đáp số : 21

​ nhé ^_^

​

I. Write /tr/, /kr/ and /br/ above the word that has the corresponding consonant cluster sound. Then, practise reading the sentences.

1. We tried /tr/ to catch the train /tr/ to Ha Noi.

2. This morning I felt crazy /cr/ because the traffic /tr/ was very heavy with a lot of trucks /tr/ and the streets were crowed /cr/.

3. My father likes cream /cr/ in his coffe.

4. My mother buys groceries on credit /cr/.

5. My computer crashed /cr/ while I was trying /tr/ to create /cr/ a new directory.

6. My parents are both broad-minded /br/, so they are willing to lisren to our own opinions.

7. My brother /br/ has brown /br/ eyes and broad /br/ shoulders.

8. A breathalyser /br/ is a device to measure the amount of alcohol in a drive's breath /br/.

9. I spend two hours browsing /br/ the wed every day.

10. People feel lonely because the build walls instead of bridges /br/.

6 : 2 = 3

trong 4 gio o to do di duoc la 

42,6 x 4 = 170,4km

linh nhi o minh la ban cua ban ban ho bam cho minh nhe  thanhk you 

50:2=25

3x = 2y => \(\frac{x}{2}=\frac{y}{3}\)=> \(\frac{x}{10}=\frac{y}{15}\)

7y = 5z => \(\frac{y}{5}=\frac{z}{7}\)=> \(\frac{y}{15}=\frac{z}{21}\)

=> \(\frac{x}{10}=\frac{y}{15}=\frac{z}{21}=\frac{x-y+z}{10-15+21}=\frac{32}{16}=2\)

=> x = 2.10 = 20

y = 2.15 = 30

z = 2.21 = 42

Rewrite the sentences without changing their meaning. Use the words in brackets.

3. Sebastien is a French, but he plays Vietnamese folk games well. (although)

=> Although Sebastien is a French, he plays Vietnamese folk games well.

4. He has to join the festival in order to play Vietnamese folk games. (so)

=> He has to join the festival so as to play Vietnamese folk games.

5. Although the weather was terrible, we had a good time. (spite)

=> We had a good time in spite of the terrible weather.

6. So that Susan would be fit for the skiing, she went to the gym three times a week. (order)

=> Susan went to the gym three times a week in order to be fit for the skiing.

7. My family went to Huong Pagoda Festival two months ago. (since)

=> It is two months since my family last went to Huong Pagoda Festival.

8. You won’t get in to see the show if you don’t have reserved seats. (unless)

=> You won’t get in to see the show unless you have reserved seats.

Thương 2 số đó là:

50 : 2 = 25

Đáp số: 25

Có phải ý bạn là : \(\left(50^2+48^2+...+2^2\right)-\left(49^2+47^2+...+1^2\right)\)đúng không :)

Đặt \(A=\left(50^2+48^2+...+2^2\right)-\left(49^2+47^2+...+1^2\right)\)

\(=50^2+48^2+...+2^2-49^2-47^2-...-1^2\)

\(=\left(50^2-49^2\right)+\left(48^2-47^2\right)+...+\left(2^2-1^2\right)\)

\(=\left(50-49\right)\left(50+49\right)+\left(48-47\right)\left(48+47\right)+...+\left(2-1\right)\left(2+1\right)\)

\(=99+95+91+...+3\)

Biểu thức đã được đơn giản hóa và trở thành tổng dãy số cách đều 4 đơn vị.

Số các số hạng là :

\(\frac{99-3}{4}+1=25\)( số hạng )

\(\Rightarrow A=\frac{25.\left(99+3\right)}{2}=1275\)