đường trung tuyến ứng với cạnh huyền bằng nửa cạnh huyền. Vậy là hết :|

a. dùng csn với u1=2,Un=3Un-1. tìm ctshtq Un rồi đánh giá nó nhỏ hơn hoặc bằng 9000 là tìm đc n

b. đầu bài nói k rõ lắm. nếu như chạm sai vaò mà vị trí 2 chiếc cúp đó vẫn giữ nguyên thì chỉ cần 1 người là đc. còn nếu nó k giữ nguyên vị trí thì chịu, nhờ may mắn

Sửa lại chỗ này: \(\Rightarrow\begin{cases}x=\pm10\sqrt{2}\\y=\pm9\sqrt{2}\end{cases}\)

\(\frac{3}{5}x=\frac{2}{3}y\Leftrightarrow\frac{x}{\left(\frac{2}{3}\right)}=\frac{y}{\left(\frac{3}{5}\right)}\Leftrightarrow\left[\frac{x}{\left(\frac{2}{3}\right)}\right]^2=\left[\frac{y}{\left(\frac{3}{5}\right)}\right]^2\Leftrightarrow\frac{x^2}{\left(\frac{4}{9}\right)}=\frac{y^2}{\left(\frac{9}{25}\right)}\)

Áp dụng tính chất của dãy tỉ số bằng nhau, ta có:

\(\frac{x^2}{\left(\frac{4}{9}\right)}=\frac{y^2}{\left(\frac{9}{25}\right)}=\frac{x^2-y^2}{\left(\frac{4}{9}-\frac{9}{25}\right)}=\frac{38}{\left(\frac{19}{225}\right)}=450\)

\(\Leftrightarrow\begin{cases}x=10\sqrt{2}\\y=9\sqrt{2}\end{cases}\)

\(\left(x+y-12\right)^2+\left(y-2\right)^2\ge0\)

Dấu bằng xảy ra khi: \(\begin{cases}x+y-12=0\\y-2=0\end{cases}\Leftrightarrow\begin{cases}x=10\\y=2\end{cases}\)

Vậy:...

1. The Great Wall of China is the world's longer structure

=> The Great Wall of China is the world's longest structure

1. I swam in the sea last Sunday
I went swimming in the sea last Sunday.

2. It is unsafe to go out alone very late at night
Going out alone very late at night is unsafe.

3. It is intersting to learn English
Learning English is interesting.

4. Linda thinks it is a good idea to go to Nha Trang by train
Linda suggest going to Nha Trang by train.

5. He often participates in outdoor activities during his summer vacation
He often takes part in outdoor activities during his summer vacation.

\(\frac{x+2}{327}+\frac{x+3}{326}+\frac{x+4}{325}+\frac{x+5}{324}+\frac{x+349}{5}=0\)

\(\Leftrightarrow\frac{x+2}{327}+1+\frac{x+3}{326}+1+\frac{x+4}{325}+1+\frac{x+5}{324}+1+\frac{x+324}{5}+1+\frac{25}{5}=5\)

\(\Leftrightarrow\frac{x+329}{327}+\frac{x+329}{326}+\frac{x+329}{325}+\frac{x+329}{324}+\frac{x+329}{5}=0\)

\(\Leftrightarrow\left(x+329\right)\left(\frac{1}{327}+\frac{1}{326}+\frac{1}{325}+\frac{1}{324}+\frac{1}{5}\right)=0\)

Vì: \(\frac{1}{327}+\frac{1}{326}+\frac{1}{325}+\frac{1}{324}+\frac{1}{5}\ne0\)\(\)

\(\Rightarrow x=-329\)

Tomatoes are 25.000 dong .

->Tomatoes cost 25 000 dong

Our recess lasts for thirty minutes .

->We have a thirty-minute recess

Students have a Tet holiday that lasts for ten days.

->Students have a ten-day Tet holiday

They have two vacations that last for two weeks

=>They have two a two-week vacations

In my timetable , there isn't an English class on Friday

-> I have no English class on Friday ( in my timetable )

1. Rewrite the following sentences with the same meaning:
a. What does she do?

What's her job?
b. it's difficult to find an apartment in HN now.

It isn't easy to find an apartment in HN now.
c. Nam is the tallest boy in my class.

No one in my class is as tall as Nam.
d. your laptop is more expensive than his laptop.

His laptop isn't as expensive as yours.
e. there are three bedrooms in my house.

My house has three bedrooms.

f. have you got a cheaper book than this ?

Is this the cheapest book you have?

g. mount everest is higher than any other mountain in the world.

Mount everest is the highest mountain in the world.

h. it is necessary to learn english well.

Learning English well is necessary

i. we should get up early everyday.

We shouldn't get up late everyday.

k. going swimming in the summer is very interesting.

It's very interesting to go swimming in the summer.

2. fill in the right form of the words

a. english is an interesting and importan subject. INTEREST

b. the most populer after school activities in our country are football,badminton and basketball. ACT

c. the cards in the library are in alphabetical order. ALPHABET

d. when we come to the library, the librarian shows us how to find the books we need. LIBRARY

e. the library in our city has over 50 employees EMPLOY

f. His father is a driver DRIVE
g. there is a new equipment in the laboratory. EQUIP

h. we are waiting for the arrival of the plane. ARRIVE

i. they are friendly with each other. FRIEND