1. You must do this test carefully

-> This test must be done.

2. Many students wore jeans in 1960s

-> jeans was worn in 1960s

3. People call Chicago 'the windy city '

-> chicago is called 'the windy city'

4. They told me to look after the garden

-> I was told to look after the garden

5. We found the lost boy near the airport

-> the lost boy was found near the airpot

6. They're going to rebuild this bridge

-> this bridge is going to be rebuilt

7. We should save water and electricity

-> water and electricity should be saved

8. We saw her son 20 minutes ago

-> her son was seen 20 minutes ago

9. Someone broke the windows of the shop

-> the windows of the shop was broken

10. People don't speak English in this country

-> English isn't spoken in this country

11. We have to finish this work today

-> this work have to be finished today

12. They're going to sell that house

-> that house is going to sold

13. People used to do this work by hand

-> this work used to be done by hand

ta có 1005 chia hết cho 15=>1005*a chia hết cho 15

2100 chia hết cho 15 =>2100*b chia hết cho 15

=>1005a+b chia hết cho 15

tick mk nha

\(\dfrac{x-1}{x+2}>0\)

\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x-1>0\\x+2>0\end{matrix}\right.\\\left\{{}\begin{matrix}x-1< 0\\x+2< 0\end{matrix}\right.\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x>1\\x>-2\end{matrix}\right.\\\left\{{}\begin{matrix}x< 1\\x< -2\end{matrix}\right.\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x>1\\x< -2\end{matrix}\right.\)

Vậy x > 1 hoặc x < -2

Giải:

Gọi quãng đường 1, 2, 3 là \(S_1,S_2,S_3\left(S_1=S_2=S_3\right)\)

Thời gian đi hết đoạn đường AB là:

\(t=\dfrac{S_1}{V}=\dfrac{S_1}{48}\) ( s )

Thời gian đi hết đoạn đường BC là:

\(t=\dfrac{S_2}{V}=\dfrac{S_2}{36}\) ( s )

Thời gian đi hết đoạn đường CD là:

\(t=\dfrac{S_3}{V}=\dfrac{S_3}{24}\left(s\right)\)

Vận tốc trung bình trên cả quãng đường AD của xe là:

\(v=\dfrac{S_1+S_2+S_3}{\dfrac{S_1}{48}+\dfrac{S_2}{36}+\dfrac{S_3}{24}}=\dfrac{3S_1}{S_1\left(\dfrac{1}{48}+\dfrac{1}{36}+\dfrac{1}{24}\right)}=\dfrac{3}{\dfrac{1}{48}+\dfrac{1}{36}+\dfrac{1}{24}}=\dfrac{432}{13}\) ( m/s )

Vậy...

\(\dfrac{1}{2}x^2y^2\left(2x+y\right)\left(2x-y\right)\)

\(=\dfrac{1}{2}x^2y^2.\left(4x^2-y^2\right)\)

\(=2x^4y^2-\dfrac{1}{2}x^2y^4\)

\(\left(x^4-x^3y+x^2y^2-xy^3\right):\left(x^2+y^2\right)\)

\(=\left[\left(x^4+x^2y^2\right)-\left(x^3y-xy^3\right)\right]:\left(x^2+y^2\right)\)

\(=\left[x^2\left(x^2+y^2\right)-xy\left(x^2+y^2\right)\right]:\left(x^2+y^2\right)\)

\(=\left(x^2-xy\right)\left(x^2+y^2\right):\left(x^2+y^2\right)\)

\(=x^2-xy=x\left(x-y\right)\)

11+13=24

11 là số nguyên tố

13 cũng là số nguyên tố nên hai số dó là 11 và 13